Tarus, if you're willing to risk under $20 US, I've bought a Cree LED drop-in which works very well in my Surefire Nitrolon G2, from these guys:

http://www.dealextreme.com/products.dx/category.917
The drop-in goes into the surefire WITHOUT the spring. And, the head doesn't screw down the last full turn. However, I find no loss of water resistance even so.

I've also bought 1/2 dozen of these:

http://www.dealextreme.com/details.dx/sku.1993
they're remarkably small and bright. Others have complained that they're not too durable, but that is not my experience. My ham-fisted hunting buddies loved them... and haven't screwed them up. And, they're so small I EDC carry 2 rather than backup the LED assembly. Runtime on ONE AA is very long. In fact, my Surefire is now the stow-away and not my EDC
They're not $100 plus units. But they do fine for me. YMMV

The dealextreme folks are a bit strange to deal with, so be quite patient. They pay shipping, but ship via Hong Kong post and airmail. Just wait... it'll get there eventually.