Unless you have a SERIOUS hankerin' for another hotwire, you might get more interest and experience out of doing a Lux III mod with your other 3D Mag. You could either do a direct drive mod or if you're feeling up to it, you could do one of the mods with 3 Luxes in a heatsink made specifically for the purpose.
For the single Lux mod, you'd need a Lux III emitter. For longest LED lifetime, I'd probably go with a T**L emitter. Then you'd need an O-sink or hotlips heatsink and something like Arctic Alumina which is a thermal grease/epoxy that holds the emitter in place. Some folks also put it between the heatsink and the body of the Maglite. Other than that you just need a hacksaw to cut down the reflector, a soldering iron, some decent wire and the instructions on how to do it. Pretty easy... just take your time and read the instructions.
For the Tri Lux, you need the specific heatsink called the Perfect Tri Sink. Then you need three matching Lux III stars. (I actually built one using nice Lux I stars for better runtime, but most CPFers will no doubt get more enjoyment out of the Lux IIIs.) Then you need three IMS20mm reflectors. I wire mine in parallel so it takes a bit more patience on the soldering front, but not a big deal. This thing throws a HUGE hotspot and is very usable outdoors. Gets a bit better runtime than your ROP will too... Other than that, you need the same tools as above.
Edit - changed IMS27 to IMS20 to avoid confusion.
