bstrickler
Enlightened
If you pick a 18650 light in the end, just make sure it can take CR123s/16340. Some 18650 lights like SC600 don't. You want her knocking on your door with fire in her loins, not on them.
Fixed that
On a serious note, though...
I EDC a Surefire U2 in my pants, and have no problem with it.
The biggest decider is a few things...
Does she wear those pants that have shallow pockets? If so, then a Solarforce L2m with ManaFont's SKU 5720 with an IMR 16340 would be your best bet, although the problem would be a VERY short runtime (about 6 minutes on high).
If not, then look at the 4Sevens Quark CR123^2 turbo for $70 ($35 if you use coupon code "VOTE2012" before November 6th)