My first thought would be to find a device that has the same size screen as you're using, and just get a screen protector for that. Unless your screen is especially unusual, there's got to be something that's the same size pretty widely available, and there's a billion ebay sellers who sell screen protectors for every device under the sun.
Barring that, I would imagine that you could get the adhesive off of a typical gorilla glass screen protector without too much work - just get it hot and scrape it off with a razor blade. Cutting gorilla glass strikes me as the more challenging part of the equation - seems highly unlikely that it would break cleanly with a standard glass cutter, at least.