You can get them from Internation Medical Equipment cat #370085 30mm dia $33.00 and #370086 45mm dia $43.00 each OR you can get tem from Thermo Electron Corp cat#8002 29mm dia for apprx $22.00 (they are alittle long, but you can cut them down with a hacksaw). I had a fellow in facililties do it for me. Robyn OHSU