Ummm.....MOAB's are my absolute favorite....you are correct in that they rarely seem to come up for sale used. I've been fortunate enough to come across 2 lefty's over the past year or so that were very close in specs (53# and 54# @ 28"). I have a lead on another, but am unsure if it will pan out.
A bow that is a similar shooting experience is the Toelke Whip. Not hardly as much speed, but just as quiet and dead in the hand.
My recommedation though, go with a MOAB. The 60" MOAB has it all (62" doesn't get as good reviews, but I've never seen a lefty 62").
Good luck and let us know what you decide.
Ken