Goggle “match mod minimag” for lots of info, main article is this Match's Mods: 15min mini mag mod .
You need to populate a P90 pill with the emitter and driver. For 2×AA, use https://www.fasttech.com/p/1127402 for the driver, and your choice of emitter (recommend XM-L2 for efficiency and fitting to a TIR lens). Speaking of TIR lenses, Amazon.com is a nice 15° TIR with a shoe that fits XM-sized emitters perfectly and is 21mm for the perfect MiniMag fit.
Get a 20mm drill-bit to drill out the head somewhat (see the above thread), to fit the pill+lens (or reflector, if you choose), and you’re pretty much done.
The shoe for the TIR lens also fits other 20mm TIRs, from 5° to 120°, so they’re easily swappable whether you want flood or throw or something between.
Be aware, bare TIRs without that shoe will flop around in the retaining ring and NOT be properly spaced or centered atop the LED.
Or you can drill, sand, and otherwise fold/spindle/mutilate the come-with reflector for use with the LED, your choice.