Looking for the good P7 Malkoff mag power source...

I'm planning to get a 3 D Size Mag light for duty use and install a Malkoff P7 LED module in it. The problem I've been coming into is the power source

It requires 5.5 v so I can't just use 3 NiMH D cell batteries...so the only ways I can think to power it would be a 9 AA holder for NiMH cells of 2500 mA per cell kind like this here: https://www.candlepowerforums.com/posts/2849142#post2849142

-or-

some kind of jury rigged 18650 Li Ion Holder, with 3 cells in series.

No there is some kind of Li-ion cell in D cell form factor I saw at Kai Domain, but it's unprotected and I'm not quite sure how to charge it. Would soldering on a protection circuit work? If so, it goes back to how to charge it, what would be the best way? I've used the search function and could only come of with vague solutions to all these questions.

So what are the options for me here guys? I would prefer the 3 D Mag form factor best because in an emergency only I could use it as a weapon and also it would be easy to tuck under my arm pit to hold it. Also, I'm expecting ~20,000 lux--would that be achievable with this type of setup?

This forum is tops! Thanks in advance everyone!

FWIW, another option to think about... I was also considering the P7 drop-in after great experiences with my M30W and M60WF, but went another route.

Last week I had nailbender mod a Mag 3D for me... and the end result is fantastic!

I had him put in a warm-white DSVNI-binned P7 (he also has some really bright DSXOI-binned P7's, but I wanted something warmer), a BriteLumens Super P7 heat sink, and a programmable d2Flex direct-drive with dimming board.

He installed the LED/heatsink, UCL glass lens, modified the switch for momentary contact, and made it compatible with flat-nose batteries. All wiring is silver-coated mil-spec Teflon. Everything is epoxied in place and is VERY solid. The focusing ability of the 3D head is maintained, so the beam can be very floody or focused to a nice hot spot.

I use three 12000 mAh NiMH D-cell battteries from Battery Junction. I haven't measured it myself, but Dave said it would pull between 2.8A - 3A with the NiMH D cells, so it will run for a long time even on full brightness... and regular alkaline D cells can be used when necessary.

I don't have any way to measure the OTF lumens, but it is VERY bright!

The d2Flex is really sweet... from off, a quick press of the button will turn the light on at the previous level or at the "Forced" level if the Force option is enabled... or, pressing the switch for longer than half a second but less than 1.5 seconds will select the nightlight illumination level which is great for preserving night vision.

Dave was very helpful and answered all of my questions. If it's something you'd consider, drop him a note.