Commercial vinyl shops can help you out.
For small projects, it is still a little pricey, but they usually offer the best solution.
For my SCUBA tanks, my MOD markings (70, OXYGEN 20), I did a white background with black lettering. Commercial vinyl sticks like crazy...I've had zero peeling. For my AL40 that I switched from a "70" to "OXYGEN 20", it actually peeled some of the paint off when I removed the vinyl...brand new tank that was only a few months old!
Gluing geek since 2007