I built one of these DIY Sun Guns this afternoon. I bought the cheapest 12v drill I could find and cheap (35w MR16) halogen downlighter, 10 minutes work and now have a very bright swirl finding torch. Better bulbs are available but I wanted to test the basics first. Total cost was half that of the Brinkman
I'm going to build mine (from your step-by-step instructions links :dblthumb2

with the same halogen lamp that the 3M Sun Gun uses....the 35w color-corrected, full-spectrum, halogen lamp, along with a miniature ceramic lamp base, when the parts arrive.
Since I'm going to use an old drill I had lying around, and the batteries and charger are no longer usable, I'm going to hard-wire it with a 120v-12v convertor (from an old computer set-up) with a 30ft cord length.
Total Cost (USD): $10.93
-Drill(with carrying case)...............$ 00.00
-Replacement Cord....................... 00.00
-Halogen Lamp............................. 7.95
-Lamp Base (socket)..................... 2.98
When I find a really cheap-priced drill, I'll make a more portable one with the 12v battery/120v-12v set-up. I'll just have to get another lamp base. May try it with the 50w lamp for comparison sake, though.
Again I say thanks for your informative posts.
Bob