As for a replacement, you can go with cnn.cn. Theyr cheap, but its overseas, so takes awhile. I found some on amazon a bit ago too, and I'm sure theyr on ebay as well
I bought some as spares from eBay, they are OEM, and fit perfectly. I'll leave the one I removed soaking in isopropyl alcohol for a few hours, let it air dry. That way i'll always have a fresh one ready. Good Luck!!
i decided to give my old trackball a good cleaning today.
a spot of dawn and some warm water in a glass. soaked for 5 min, rolled the ball in every direction. rinse (almost lost it down the drain, so be careful), dry. works like a charm.
i relate it to the ball and rollers in an old-fashioned mouse getting gunked up.