PP carries it. Look at Clasps and Findings, then Misc. findings. It's $60 and I think about 7mm wide. I thought I saw Bellafindings.com having it too but their search engine is really weak and did not show up at all (I tried rondelle and roundel, they spell both ways on their website). You can call them to be sure.
I found this page from Tripps (I buy from them when setting my own faceted gemstones), not gemstone rondelles, but they do have plain 14K beads and rondelles. I thought $39 for a pack of 10 was a decent price. They also have earwires (cheap) and stuff for earrings.