Any polyester tape or film would work. For sandcarving flat substrates I use Lazer's Edge Tape from Specialty Tapes (FAST). It can also be acquired through JDS Industries. It is red in color.
I have never used etching cream, so have no idea if lasering through the standard films would leave an adequately cleared surface for cream application. You may discover that the result of cream etching of laser engraved glass is as awful looking as plain old laser engraved glass.