I've been using a NuArc 26-1K mercury exposure unit that has a vacuum frame about 2' x 2.5'. It was donated to my place of employment but I've seen similar units go for a couple hundred bucks on eBay. It may be overkill for your needs, but I like the fact it has a built-in integrator to monitor and adjust output. It's noisy and has about a 3' square footprint, but otherwise no complaints.

Joe