Solitaire thread help

I just finally decided to get a solitaire to play with and modded it based on this article.
http://www.flashlightreviews.com/mods/solitaire.htm

I can't leave well-enough alone, so I've decided I'd like to cut down the light so the extra spring isn't needed. Judging by eyesight only it looks as though I wouldn't need to bore out the tube, and I could just tap new threads into it without much difficulty. (that's just a guess)

My question is does anyone know the correct sizes/thread counts for the tap that I'd need, And a suggestion of where I could get it. Thinking home depot probably won't cut it.

I've seen taps at our local TrueValue hardware store (or was it Ace?). Anywho... I'd take the tailcap to the store and make sure the threads match the tap I was looking for. You gotta post pics of the cut-down dude.