Have you tried a hot tub and spa place? We have to replace the rings on our hot tub once in a while. I would also try plumbing supply places

Thanks. I'll try that approach, though I don't know the brand name of the tub.

Since you have the pics, I would talk to the places over the phone, send the pic in an email and the dimensions. They will probably ask for outside and inside diameters, etc. Do these come off easily? I know some come off for cleaning purposes, etc. If they do, just take them in. I am guessing that as long as the inside part fits, if it's a little bigger on the outside trim that would be OK. Smaller may show some colour difference on the tub's shell itself.