Steve, check this guy out:-
I have one of the whole plate models, but he is making other formats. This is BLACK Acrylic, it's tough, and has a spill proof lid. It will still leak a little if the bath was completely inverted, but I can vouch for how good this thing is. I actually think the whole plate version might work for 8x10 plates aswell if you keep a really good eye on levels as the internal dimensions are 10.75" x 9" x 0.75"
I am making a bath holder for this for use in a dark box, and then I can lift it out and use it in my darkroom with the built in fold out stand when I need it.
I think it's a slick product indeed.