I have looked on the Pearl Factory website (where we purchased these in 2011) and yes they are available. Be aware that their prices are higher in price than some of the settings from Disney. I think that setting cost me almost $200.
Just there a couple weeks ago. We picked a pearl @ Universal Studios at Pearl Factory. Grandkids picked the oyster and they looked for the darkest and ugliest one. It was a 8mm silver pearl. They were so excited. I didn't get a setting there. I waited until we got home and had it set at a Jewelers store. It's in a beautiful pendant. I would put a picture up but can't figure out how with my iPhone.
Also saw some questions about the oyster itself. They do not allow folks to eat the oyster. I believe it's because one they are not eating oysters and two they have not been probably maintained (temparature/water).