I don't know its name, but you know, in Boss pedals there is a screw to open the battery compartment (by your fingers, not by a screwdriver). And there is that plastic washer, oval shaped, that the screw is going through, at the pedal body. First does that have a special name? And do you know any online retailer selling this part? Thanks
find a guy who repairs Boss pedals, they often have spare parts... my guitarist "repaired" two Boss pedals this way... for free
Rubber, not plastic. Grommet, not washer. Available at any half way decent hardware store, although you might need to search around a bit for a good fit - take one to compare, buy more than you think you need!