[Roger]

Maybe wait until Building 19 has them? They were selling the tubes last year after the competition was over -- maybe they'll sell the trackballs this year.

(Just because I didn't feel like starting a new thread about this, I'll put this here: Bldg 19 had another ad for the rings back in April this year, and they did have a small box of them in Norwood, for $1.99/each ("their price $4.99"). "Swim Tubes" they called them in the ad. "This company develops robots and has a big cometition every year. They buy these swim tubes and use them as bumpers in the competition. This year they bought a bit too many. Because this company doesn't sell swim tubes they practically gave them to us. Assorted colors - at least 3 colors per store - 30 inch diameter - 3mm thickness". Which is odd, because we did use these tubes as bumpers on our old robot to bang around with.)