Here are a couple of quick links:
Pearl Paradise,
9-10mm AAA SS studs, plus I believe they have a 15% off special going on now. These are top quality SS pearls, which makes a big pricing difference:
For comparison,
9-10mm AAA freshwater pearls, also from PP. Much cheaper than SS:
Here's
PP "Freshadama" their gem grade, a step up even from AAA. 9.5-10mm.
The Pearl Society didn't have any SS studs that small right now from my quick search. They're known for HUGE pearls, often not totally round, etc. And of course you can check the rest of the vendors listed. I second all that cmd listed except for American Pearls. I don't have a complaint about American Pearls and haven't heard anything against them either, I've just personally never dealt with them.
Keep in mind that they might all use different grading systems. Also, even when two companies use the same rating letters, different vendors have different meanings of what constitutes, for example, AAA or AA quality.
You might ask for email photos to compare and/or consult us on those photos and etc. We love to see pics and also to give our opinions.
Unless you have your heart set on South Sea pearls, if it was me I'd probably go with top grade freshwaters instead, due to the large price difference and not being able to tell the difference. Good luck!
P.S. If you want one pearl for a custom made frog pin, you can contact them and ask to only buy one pearl.