Mountain electronics carriers the Zener mod kit for Qlite drivers that powers 6 volt emitters using a 2 cell setup. Available either in a DIY kit if your comfortable soldering small parts or Richard(Mountain Electronics) can mod a driver for you.
You may have to upgrade or do a spring bypass on...
The fw3a glass measurement are 23 x 1.5mm. Flashlightlens dot com have several in stock that should work. Nealsgadgets offers a sapphire replacement lens that should withstand more abuse than a glass lens, but would take a couple weeks to arrive