Lately, I have been using a clean 5-gal. bucket for a print washer. Just drill some small holes in the bottom. Let the water hose run slowly into the top.
Stand prints up vertically. Curl them around the sides of the bucket, emulsion facing inward. There's enough room to wash two or three 11x14s. Maybe five or six 8x10s.

So, what if you didn't drill holes in the bucket and filled it full of water? You could fit the snap-on lid onto the bucket.

Okay, so that would be heavy as hell... What if you used a Tupperware or Rubbermaid container with a snap-on lid?

I don't know... Just spitballing.