Found these on ebay:
http://www.ebay.co.uk/itm/230984458411?ssPageName=STRK:MESINDXX:IT&\_trksid=p3984.m1436.l2649
Might be useful for getting 4D power from a 2D Maylight etc, or you could use 2 in a 1D flashlight maybe?
I bought a few from batteryjunction.com a couple years ago. They had a dark green wrapper. I think these are a different brand. I’ve been happy with them. They are slightly longer than 1/2 of a regular d cell though. I’ve used 3 in a 2D Mag for a Mac’s Customs drop-in. If you shortened the spring you may be just able to get 4 in a 2D. Five of them fit perfectly in a 3D Mag body, and in fact the Mag Charger and old Streamlight SL20 battery packs are 5 1/2 D cells wrapped together. I don’t think battery junction has them anymore. That price seems a good bit higher than I remember paying for the ones I got.
$20 ea. with the shipping? Wow!
hmmmmm, might get some of these, I’ll get em fast! Same price.
Item location:
North Las Vegas, Nevada, United States
Ships to:
Worldwide See exclusions
Price is high isnt it. Pity.
I could not beleive myself i never saw one of this before, very expensive though.
I have 4 of them that I bought about 2 months ago from batteries in a flash. They work well. hold the voltage under a heavy load(actually a little too good). They charged to over 3000mah from when I ran them out. I’ve never done a measured discharge so I can’t say for certain about capacity. You can get 4 of them in a 2D mag but it’s tricky.
Hello Minos! Welcome to the forum. I like flashlights too! 
How would 5 1/2 cells do in a 3 D cell stock LED MagLite? Will it go poof or just be that much brighter? How about runtime? Longer than 3 D cells?