A good "drop-in" LED mod for a Tec-40 would be something like an EverLED, or one of the other PR base luxeon modules. One idea is that you can pick up a Craftsman 3XAAA 1W luxeon lights at Sears for only around $20.00 or so, and take the PR based luxeon module out of it and put it in your Tec-40 (just make sure you use only 3 AA cells and a dummy cell...the module is direct drive and the 6V from 4 AA cells will either make it go POOF, or make it run way too hot, seriously degrading it's life). At $20.00, the entire light costs less than most "specialty" PR base luxeon drop-ins, and generally speaking the tints of the luxeons in these Craftsman lights are VERY good. I've bought four of them and have yet to get one with a bad tint. Being a digh dome (...or Lambertian), the Tec-40's reflector should work quite well with it; and running DD off 3 AA cells it will be quite bright and have a VERY respectable run-time! Hope that helps!
PJD