I think they are very common. I have seen two different ones in Virginia (I bought one) and at least three different ones in Wasington.
I think a few other Sega games came in the same cab as well. I have seen two cabs converted to other games. They have a vertical 19" monitor and an isolation/step down transformer that has a ton of output voltages including 9v, 12v, 18v, 100v, and 120v. The original monitor runs on 100vac and is in a unique frame as well.
I ended up giving mine away to a guy who was going to convert a Gobbler cocktail to a 60 in 1. I figured converting the common Sega was a lesser sin than converting the only Gobbler I have ever seen and he preferred the Sega control panel configuration and larger monitor space.