The problem is that most vendors won't want to take the risk of putting two blennies of the same species into the same tank to test pairs. They'd lose money since a number would be killed off or fail or just be a waste of time. It is possible to pair Midas blennies; I've seen it on a breeding website. Again, the problem will be cost since that species is much more expensive than, say, a bicolor blenny.
I think it would be sweet to have a pair of Midas blennies. You'd want to check with people who've done this before - who knows whether they may become very aggressive once they start spawning? (MOFIB or MBI websites are good sources).
If you have a friendly LFS that will let you fool around a bit, ask to try pairing blennies in their tanks. Just remember that bicolors are much cheaper than Midases when you may have to buy 4.
