Hi I think it's the gas tank black rubber seal, but I have seem to misplace mine, any alternatives? I'm sure I can find something in the hardware store or maybe buy one online here
If you're talking about the trim you can get by with thin rubber tubing cut length-wise (so it has a C shaped cross-section) and just "clip" it on. If it looks good consider gluing it.
Used to do this in high-school/college with drums that don't have bottom heads, like concert toms and marching quads/quints/hextets, to protect them when they are placed on the ground.
Cheap alternative to the "right" way to fix it.