For mine i used 1" PVC filled with sand, and being the eggcrate is a little rough and sharp i grabbed plastic mesh (BirdBlock) you'd use to cover your plants with.. I just zip tie that to the pvc frame.. Plus i have plenty of water flow through the mesh.
Could you use acrylic? Two piece like 2x2. Drill a bunch of holes in one piece (the actual divider) then glue like 6-8" wide pieces on all sides... Fill in the rest of the bottom with black acrylic to hold the divider in place.