I think Fay Cullen has a lot of ruby halo settings. Perhaps they also have ones with a halo of diamonds around it. I've never worked with Fay Cullen before, but I've read things about their return policy. It might not be the best, but I defer to others who have worked with them.
I would look at www.EstateDiamondJewelry.com.. I have seen that type of setting there. You could find one with a diamond
in it at NewYorkEstate Jewelry too. Good luck!