I cut the circle on my table saw. Do this at your own risk as the table saw is a dangerous tool.. There are videos in youtube showing how to do this but anyway I'm uploading my photos here. I started nailing a nail at 62mm from the saw kerf in a small table saw sled. Then I cut the nail head and filed it to a point. I cut a 65 mm square from a piece of MDF and draw the diagonals to mark the center. I pushed the square center over the nail until it seated fully on the sled.
Nice idea though.
In place of the wood, some sore of high density, stiff foam might work (could be cut, trimmed etc. with a knife.
This one would certainly get my vote. And the idea is just as adaptable to other clear bins (food containers, storage tubs, etc.) Gonna have to break out my loose router and drill bits and get cracking on this!