After playing one of these over at bintzknocker's a couple weeks ago, I went on the hunt for one. Found several in collector's hands, but no one wants to part with them (and I can't blame them; it is a very addicting game). I did find one available on the East coast, but with shipping, it was going to be a bit pricey. Then I managed to find one here locally that I could purchase, so I jumped at the opportunity. It's mostly complete, does work, and has some cosmetic issues to address down the road (including some non-original touch-up additions). Overall, not too bad though, considering it was used on location as late as 1995.
I do think it would be worthwhile to continue to watch for them and snag when possible.
So now I have a lone Bally "EM" among a bunch of Gottliebs.