This may sound a little crazy but I was at Home Depot a few days ago and I saw a perfect darkroom sink for what I need. It was a molded shower pan of good quality. It was only 5 feet long x 36 inches wide but tappered in depth form about 3 inches to 6 inches down its length with a drain at the very end. This could be fitted very easily into a counter top. The best part is, it was only $175. That is cheap.