If you’re in a big hurry, you can probably get paper masking material at a local sign shop. I’d call ahead, but any shop that does vinyl signs or acrylic signs will probably have “paper transfer tape”, which is a generic term for it. They even have small (expensive) rolls of stuff that will work at most Michaels locations.
If you’re in less of a hurry, mail order is one way to get exactly what you need. This might be helpful, check out #2: