I cut a small square of soda can out with tin snips, sanded it to a thinner measurement and pierced it with a tiny needle. The frame box - I just made up that term, so don't hesitate to correct me - was milled out of ABS. I actually did a lot of work by hand, simply with a file. I hand-threaded the holes for the screws. Finally, I cut and inserted the O-ring into the grooves to make it light-tight. Feel free to use my photos or copy the design. If you are interested in creating one for yourself, I could draft up the measurements and write up some directions to help you out. When I get the time, I'd like to make several more in different body configurations just for fun. It would be great to see what you can come up with, as well.