Yes! Look on ebay for loose Swarovski Chatons
these are pointed-back glass rhinestones. The size you will need will be the small size, this can be described as "ss" (stone size) or "pp" (pearl plate)
I forget the actual size that you need (Don't have a pony to hand to check) -
I believe SS12 or PP18 is the size you need.
(Thanks, TRTL!)
please measure the diameter of the space and then look at the chart below:
https://imgur.com/a/NT7sKLl Do not use superglue, the chemicals dull the foil-backing and leave you with a foggy jewel! Epoxy resin is safe, in my experience.