I made a set of them out of plexiglass. Actually I should say I had the plastics shop make them. Once I figured out the materials cost their labor was almost free. Mine are about 12.5x15.5 inside dimensions and about 1 inch across for each slot. They hold about 3 liters each. Over time the sides have started bowing on the outer tanks (I keep them all strapped together) even though they are made from 1/4 inch plexi. I used the Nova clips to hold the paper. Sometimes the paper sticks to the smooth side, but not badly. The biggest problem is the developers leave deposits on the sides which require frequent cleanings or you get stains on the print edges (I never had it stain the image area for some reason).

If you are short on space a set of three 8x10 tanks should cost under $100 to have built and be easy to use. I would still use a 1 inch wide slot so the clip and print have room, even though this will take you up to about 1.8 liters per tank.