There isnt a vendor that specializes in mini-orchids that I am aware of.
A vendor that specializes in mounted orchids is Andy's Orchids in California. Exactly where he is, my old brain forgets!
If you have access to old books or an orchid book specialist, you should get your hands on a book by Rebecca Northern. She wrote a book on 'Miniature Orchids' maybe 40 years ago. It is excellent! It would provide you with a fantastic starting point.
This is exactly why I attend orchid meetings. Old volumes often turn up on sales tables as members move or pass away.
Good luck in your search!!