Well there are a lot of o-ring manufacturers out there; don’t limit your search to flashlight places. I would think you can just google search by diameter and thickness and material.
here , but not cheap :
edit :
i found some also here :
http://www.ebay.com/itm/10x-Oil-Resistant-NBR-Nitrile-Butadiene-Rubber-1-9mm-O-Ring-Sealing-Ring-5-130mm-/231775527170?var=&hash=item35f6e5e102:m:mO5s0gCDuTEfsSqFGDuhHvw
I use copper shims under the MCPCB instead - got a kit off of eBay of lots of different thickness ones, 20mm squares - reflow them to the copper MCPCB - fills the gap nicely, plus more copper 
.
Awesome!!
I like alot that flashliht, if it weren't for its smooth reflector i would put in it an XHP50
Have you tried to visit any hydraulic systems local shop?
I think you have more chances to find unpopular o-ring sizes on them than on the internet.
Squared shims?
Do you have any link?
This reflector works well with this host and the XHP50.
http://www.kaidomain.com/p/S008833.36_6mm-D-x-25mm-H-OP-Aluminum-Reflector
It ends up being ~1.6mm shorter than the stock reflector, so an appropriate spacer is needed under the MCPCB.
I built up some to sell and the result is quite nice.
Here's one example (BLF X6 triple mod):
Another (MaxToch 2X):
Very easy to work copper with a file or rotary tool, specially in thin material.
Easy to find on eBay - search for copper shims 20mm in eBay, one example for $7 shipped of assorted thinkcnesses:
http://www.ebay.com/itm/10-pcs-20x20-mm-Copper-Pad-Shim-2-pcs-of-each-thickness
Lot of thanks EasyB and Tom E, you gave some very valuable information :D
I sold some lights over the weekend to offset an issue that had my wife quite worried. One of these was a Courui D01 with SBT-70. In testing it, the lumens output was only 1179, seemed it should be more. So I built a new ramping FET driver, re-designed the piggyback mount, re-designed the grounding system at the tail pcb where I’d put a cut-off switch in, and it now makes 1949 lumens… highest I’ve ever seen from an SBT-70! 
And now it’s on it’s way to a new home. lol Boy did I so want to keep it after it started really screaming! 
Lol I saw it before you fixed the 2 to a 1 and I was really impressed!
Yikes! Big difference. So do you think it was all a result of reducing resistance from the tail and driver mount changes?
That's a huge difference. I imagine the throw scaled the same way. Am I goin buggy or where there a typo change in the lumens?
Oops, nevermind - see PD caught it.
What’s exactly the good thing for SBT emitters (if any) ?
I typo’d the lumens, caught it and corrected it, but some of y’all read it before it leaves my mind and get’s past my fingers.
The SBT-70 has a round die, one of the only emitters that does. This results in a smooth defined round hot spot, especially noticeable with an aspheric like the JaxMan Z1, which I also have one in. They are 3V emitters with low Vf, as such they can pull a LOT of amps from a single cell but they aren’t very efficient, normally doing something in the 1500 lumens range burning 17 amps.
The large triple 18650 contact board is a press fit. Ground can be iffy through the board. So I drilled and tapped a hole in the big copper sink I got from RyanSOh for this Courui, attached it to the driver board on the inside to fortify ground. When I initially built the clicky switch onto the rear pcb I didn’t have correct screws so I used solder blobs as stand offs for the screws I had on hand that were too long. I now have a lot of shorter SS screws so I removed the solder blobs and used correct length screws to get a good solid ground on the tail end. Retouched the soldering to the big Omten switch, and it all paid off. I’m thinking it’s pulling over 20A from the 3 LG HE4 button tops.
SBT-70 emitters have a perfectly round hotspot…my idea SBT-70 emitter would be in a really good zoomie host…no square when zoomed in.
Big, expensive and not all that efficient, but hey, the die is round so in an aspheric the spot is round! :party:
They’re also pricey. Discontinued now and difficult to find, they were around $70 per emitter. They have a beautiful bridgework of bondwires that is unprecedented in the emitter world, I like em for all these reasons as well as the unique High CRI Daylight white tint that was once available.
This is as seen in my Jaxman Z1
Oh yeah, they come with an AR coated thin glass window pane on a silver metal frame that sits flat, rather than a dome. I like removing this pane for better output. The one in the picture above has the frame and glass pane removed.
Thanks people .
And another question … If i have an emitter with a fairly high Vf and a fet driver , using 2 or 3 batteries (edit :in parallel ofcourse) will make any change ?
With the proper Buck driver, yes. An XP-G2 can’t pull high amps from a single cell, but with 2 cells and a Buck it can easily do 5.5A or a bit more for some 1100 lumens. The tight beam from a de-domed one is the preference here, in a large reflector or aspheric, for throw.
Answer to the parallel question: yes. If the delivered current per battery is halved, the battery is at a higher voltage. With more voltage, the current goes up until there is new new balance.
Thanks again Dale and Jos for your answers .
Losing it. Totally overlooked the parallel part of that. Ugh.
The Courui D01 is one example where multiple parallel cells really helps overall. With a large diameter reflector it’s easy to put a de-domed XP-G2 in there for some really sweet beam profile action.