lol - I have no idea about ring sizes but did you try ebay ? and a friend just told me about another site - i'll see what it's called - I haven't been on it yet....with all the jewelry sites I can't believe you can't find what you're looking for....
I don't know what a morganite ring is but sounds like you want it bad -
ps...edited to add it's called
http://www.esty.com/ but don't konw if they sell jewlery
did you try yahoo and HSN ???