There is an unending supply of sponge holders on Thingiverse, but none of them clipped to the edge of my slop sink they way I wanted. This sponge holder is designed to clip to the inside edge of a Sears slop sink, which in my case, has a 0.4 inch thick rim. It's designed to hold a sponge that's up to .6 inches thick, with a little extra room to get the sponge in without too much trouble.

I printed mine from PETG so it would flex a bit without cracking. Had I thought ahead further I would have designed the holes with printer overhang in mind. On my printer, the diamonds come out of without support, but they don't look the best.