I got a set of CB500 rings from Cycle-Recycle last year. Standard rings were not easy to find. The only downside was that they were mis-adressed and floated around in the postal system for over a month before being returned to Cycle-Recycle and the mistake was corrected. Top end gasket kit is the same as a CB550. I picked up a set of Athena gaskets at Bike Bandit, and have had no problems. Came with the pucks too.