Hey, Cableguy --
While this may not be the greatest of help, here's what I did to keep from paying over 400 bucks for a tin box -- of which even the largest size available is way too small; for both the cost AND the utility.
I bought a Black and Decker base cabinet (any brand is fine, Rubbermaid, etc.) made from polyvinyl -- it has two doors that make a good seal when closed and includes an adjustable shelf, too, which comes in handy -- a dryer vent kit, and a ceiling exhaust fan, one in the mid-price range, about 25 bucks are the other two things needed. Cut a hole in top of the base cabinet, mounted the fan, hooked the vent kit up, and vented it out one of my hobby room windows -- a set-up exactly like venting a clothes dryer. The polyvinyl cabinet is a snap to clean, as any overspray which doesn't permanently change the color inside the booth is easily vaccuumed right out with a portable shop-vac using a brush attachment. The exhaust fan is cleaned the same way. The booth is very lightweight and three times the size of a "real" spray booth. Took about 2 or 3 hours to build -- my first time attempting anything like that -- I've made 2 others for modeling friends, each in less than an hout. Total cost: $65.00.
Placing the exhaust set-up in the center of the cabinet's "ceiling" has worked out great for me -- I get a nice, even pull on the entire inside, no matter at what angle or how much I'm spraying -- plus, I have the option of leaving one of the doors closed, for even better removal suction.
Hope this might be of some help, or at least spark a few more ideas --