The best place by far to get a vector monitor is local and cheap!

I lucked into mine. A tech I use at a local distributor told me that one of his coworkers inherited a space duel he didn't want, so I gave him $200 for the monitor. He though I was nuts!
Good advice about RCVAC/M. Before I got that deal, I was going to get one from one of the posters there. More expensive, but they ARE out there.
Be warned. My wife put it best when she observed, "That thing is a money pit." The ZVG board alone was $240 (Zektor is currently out of stock, but more are in production). And of course, the monitor. Vectors are very flakey and mine already is having problems so it's on the bench for an overhaul. Also getting sound to work in DOS with a PCI card is a pain (at least it was for me). You also need a proper power supply for the monitor. Other than the Vectrex, no vector monitor I know of just plugs into the wall or uses a standard isloation transformer.
Totally worth it, though! You just can't replicate the look on a regular monitor, no matter how much you crank up the brightness.
Thanks for the kind words on my choice of name, Chad. It was ---auto-censored--- hard to come up with something that didn't sound stupid to me. Vector Castle? Ultivector? Vectorcab? I think not.
Anyway, good luck to you both. BTW, i correspond semi-regularly via email with three other guys who are also building Vectormame projects. If you want in on the discussions, they have been very helpful to me.