I have gone to the three shops around here, none of the techs replace rotary valve bumpers. WHAT? How useless. I found some small, round material as a stop-gap measure, but I'm desperate. My horn uses stuff that is profiled like a ball on a plinth, and the plain round stock does not give me any adjustment. I saw a trombone piece that was much larger than my horn takes, wondering if you have any suggestions? I've tried ebay, amazon, and calling a shop I use about 50 miles away, who does not carry this profiled material either. HELP!!!!

Go to Osmun music.

http://store.osmun.com/browse.cfm/buna-rubber-rotor-stops/4,1528.html

They have all the round sizes. I know the style you are talking about. I use to use those exclusively. But I now just use the regular round bumpers. The size you need obviously depends on the horn make you are playing. If you don't know the size you need they can probably help you identify what you need. They have some very good technicians.

You can also use cork. Get a nice piece of sheet cork form a local hobby store or repair shop & use a very sharp razor blade and an emery board to shape it to the exact size & shape that you need to get your rotor to line up correctly. I worked in a musical instrument repair shop for about 6 years, and this was what we did. The cork, in my opinion, is better than rubber or neoprene because it is easier to make it conform to the exact shape & size that you need to prevent any air leaks when pressing your rotor valve.