In the mid-80's, Model Railroader published an article on building your own spray booth. I built one based on the article, using a sealed motor exhaust fan purchased from W.W. Grainger and aluminum sheet and angle purchased from Home Depot. It's been in use now for about 20 years (oh how time flies!) Total cost was about 60 (1980) dollars. Not sure what it would cost today. The whole thing is bolted together, so no special skills (welding, etc.) are required. If there is interest, I can try and find the article or work up plans from mine, including spec'ing out part sources and prices. Shown here without the filter in place. The actual opening is 20"w x 14"h.