I often repaint bikes. I take off whatever chain stay protector is there if it is chewed up. Most are made of some kind of tape. On the Fuji I just finished I was trying to think of something I could use instead of buying one. looking around the shop I saw some heavy duty duct tape on the wall. This isn't the light weight grey stuff. it is much thicker and sturdier. The Problem was how to cut it to size and shape . this tape sticks aggressively and if you stick it to itself while handling you are finished. What I needed was something I could stick a length of tape to, cut it to a tapered shape so it would fit the tapered chain stay , then be able to peal it off once it was cut. What I found that works is parchment paper, which you can find in the grocery store . it is used in baking. The duct tape sticke to it so it can be cut then easily peals off without loosing its stickiness. It worked great and should be very durable.
update
I now use "gorilla " tape and set it on a clip board, cut it with a razor knife and straight edge, pull it off the board and place on the chain stay.