I am looking for a vendor with a large selection and reasonable prices. Seeking a 6-9mm silvery star sapphire, or maybe one in an unusual fancy color. Thanks!
Try Barry Bridgestock, The Gem Trader, Dana at Mastercut Gems. MC gems doesn't have any on the web site, but I would be shocked if he didn't have some back stock. You could also try Lee Little, but I have not purchased from him and thus cannot comment on the quality of his gems. I do know that he has some stars on his etsy site, though.
So, it's not loose, nor are there lots to choose from, but OtherwiseEngaged on etsy has a fabulous five carat star for sale right now in a silvery color. I would snap it up if I heads the finds right now!
I have bought from Brad at www.thegemtrader.com.. He has a good eye. Silvery/gray star sapphires should be generally easy to find, so I think you can be picky that the star be strong and well-formed, and that the cabochon have the shape and dimensions you desire. You may also want one that has good clarity, but that is harder to find as the silvery ones tend to be very silky.
In buying a cab, you will generally pay for both the face-up dimensions and the carat weight. You can get more face-up size if the cab is not that thick/deep.