Vacuum frames were a wonderful tool in the graphic arts community, still used a bit, but nothing like in their heyday, which was the seventies and eighties. We had heaps of Nuarc swinging vacuum frames. Some of them double headers, meaning you could load the flip side while the underside was being exposed.
There may be something quite cheap available from graphic art houses or printing shops, as almost all of them probably used a vacuum frame of some sort.
I live in Australia and these things were a bit thin on the ground here, compared to the USA that is. We have quite a few turning up every now and again here, so I have no doubt there should be quite a few around your neck of the woods.
We ran a Nuarc vacuum frame under a wall mounted enlarger for contact printing B&W and colour negatives and/or transparencies, usually 8x10" and 11x14". But with the Nuarc it was certainly possible to do 24x30" as that was the size of the vacuum rubber.
I have no idea as to whether or not the Edwards Engineered product is any good, but I have viewed them online sometime ago and wondered if any made it to my country and would they ever come up secondhand and would I know about it and would I be able to purchase it? Sigh.
Mick.