Yes. Not at all common. I did a quick search and only came up with a single example of 26700 cylindrical cells for sale. This was for commercial sales with a large minimum order. But At 5000 mAh /10 Amp rating , you may as well use 21700.
Thats why i recommend the Samsung 50S 21700.
Ive had great results with it running SBT90.2 lights.
For no holds barred maximum current applications the stellar Molicel P45B 21700 is the best of the best.
It seems the 26650 market has really dried up. Two years ago there were choices aplenty for 20A cells or energy cells pushing 6000mah. Now it seems most models are discontinued or unavailable.
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There is something like this, but who knows how it works 
Would have to buy and check what it can, I have all measuring equipment, but I doubt it is something great
https://pl.aliexpress.com/i/1005005274385380.html
21700 has pretty much taken over. 26800 are still around, but i think are being phased out. They were primarily industrial application cells. Aloft Hobbies was the primary retailer in the US for the QB 26800. I got one a year or so ago for like $10? They’re sold out now. I only have 3 26800 compatible lights (2 NI03s and a Lumintop D3) and I mainly use the 21700 in them now. There’s just too many good 21700s out there now to justify a 26650 anymore. 5000 mAh 20A 21700s are common and pretty cheap and the samsung 50S and Molicel p45B are freakishly good for output and extended runtimes.
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Check the listing. 6000mah TURE capacity! (t r u e)
From an off brand Chinese manufacturer with absolutely no current rating listed anywhere.
Likely an 8 amp cell, be surprised if it could do 10A.
With delivery on NOVEMBER 27th!! Hard Pass.
For your EA01,
Id go with a Vapcell 15A CDR 5500mah 26650 instead for max runtimes. They are available for $10 in less than a week.
Or maybe this:
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Any reason why you wouldn’t opt for these if your light fits them anyway? Vapcell 26650 6200mAh 15A - K62 Battery
I have many LG M58T, but they will have too much sag under 15A. You don’t buy strong light and put battery with high sag I have many, many 21700, so maybe really will stick to them. But I think I will shoot this chineese 26700, only I will ask first what seller says about constant current. If he says 10A, then I will not even give a try.
The thing is, as of now, higher current capabilities mean lower capacity. Still, those Molicell P45B cells give you most of the capacity of the 26650 with high current capability. Want that light to stay bright… change the cells often and keep them charged up.
Maybe down the road we will get the 10 Amp Hour, 50 Amp CDR cells that you want. But it is down the road a bit.
There are such cells, but not in this size I don’t need 10Ah and 50A 8-10mOhm IR AC cell with 6000mAh+ will be enough. If there are no such or they will be too expensive, then I will stay with 21700, too many lights at home to spend 25$ on one cell for one of them.
Ah, yep! I think that this is what people have been telling you.
Though if you find something real interesting, I am sure we all would love to hear about it…
Definitely worth considering if the price is right. I’m a bit dubious of vapcell products though. I got two of their 15A 3000 mah 18650 a while back and both lost performance after a few months.
Almost no factory produces 26700 li-ion batteries
Most factories are producing cheap 26700 LFP 3.2v batteries, approximately 4000-4500mah, with a wholesale unit price of around $2
Expected not suitable for flashlights
Consider the vapcell battery, 26650，26800，21700, which has excellent performance
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Kajman I’ve got that light also, try the 26800 cell. This tube Astrolux Official Online Shop This cell 26800 Vapcell INR26800 6200mAh 25A High Discharge. Vapcell INR26800 6200mah 25A - Vapcell batteries and Chargers I use 26800 instead as the tube fit the hand better. 26800 is in two types; 6200mah 25 amps and 6800mah 20 amps. I have several of these cells are the currant rating was done at 10 amp load. I get 7200-7300mah on the 6800mah rated cell when only drawing 1 amp. Mateminco are the maker of these lights https://www.aliexpress.com/w/wholesale-mateminco.html
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That is one hell of a good answer My hands are on bigger side, so additional cm won’t matter, I think if checking 26700 goes bad way (and it seems to go so-seller can’t provide datasheet or cont. discharge current), I will do that 
Thanks a lot. I can see 26980 tubes too…
https://pl.aliexpress.com/item/1005004090253697.html?spm=a2g0o.productlist.main.3.186f21efN0QntD&algo_pvid=f480a8d6-b3d6-4fd3-870a-fbb8e6c808cd&algo_exp_id=f480a8d6-b3d6-4fd3-870a-fbb8e6c808cd-1&pdp_npi=4%40dis!PLN!71.06!70.18!!!15.98!!%402103399116952799059952045eb7e5!12000027997700626!sea!PL!878979576!S&curPageLogUid=ACoPVLqP5J1X
My S4+ has been such a great investment I always assumed their batteries would be just as good. How bad were the losses? Was your usage heavy? Just wanna know because I have 26650 lights that I will buy more cells for eventually.
My 26650 just got old, I replaced it with 21700, but I feel like not using all available space in battery comparement and capacity with it There are some 26650 on the market, but no develeopment unfortunately and prices close to new generation cells.
They weren’t used very much or abused. Just used in some modded lights with fet drivers. The losses were hige, but compared to genuine Sony VTC6 the vapcell were down on current and higher iR mainly. Difference? 10-15%, but enough to make a difference. They were similar price to the original VTC6 also after shipping from China.
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Rememeber, that chemistry gets older too Usually IR increase is first to come then. Capacity may be ok.
Sadly the 26980 has less capacity and amps than the 26800 cell.