UCL LDF at flashlightlens. For the McR-20 you want the 22.8 for the ARC4.
I don't know enough to comment, so this is opinion/speculation, but I personally wouldn't try to run more than two LUXVs to spec off that power supply in your situation - poor runtime? A possibility to consider if you like the LuxV is a pair of McR-27s driven at ~400mA, one with LDF, one clear (maybe mounted vertically?) The 29.3mm for the PM6 should fit, but I haven't tried it yet. You could have a off-low(LDF)-both switch, just like high and low beams on a car