If you go though my thread links, you'll see that I used my roll of 0.060 because it's what I have. I also have some 0.030 rolls that are too thin... at least on anything I've put together in the past 8 years.
As for not selling supplies, I would think if you called up the local glass shops and asked if they used glass setting tape on deco trim mirrors and such that it wouldn't be a big deal selling your 4 feet !