Would anyone have a rough idea on what it would cost for:
1.) Buying 1 or 2 Ideal cut stones (They seem to be only sold in lots). I just want one or 2 for a men's ring.
2.) Adding them to a ring that I supply.
You would probably have to take leftover from someone else's lot -- the merchant should have some lying around. Say $10-20 per melee, depending on size? That was a shot in the dark guess on my part...
As to adding it to an existing ring...could be hard, depends on the metal. You have to drill holes and then pull up little beads of metal to set the melee. I don't know if you can do that with an existing ring, perhaps one of the tradepeople will chime in.