If anyone is interested, I had some of the caster plates in the same shape as the print file above laser cut in 1/8" 7075 aluminum. Here is one raw (burrs and surface discoloration) and one sanded with 220>400, the edges slightly chamfered, and holes reamed. $2 a plate raw, $3 a plate cleaned up, $5 shipping for 1-4. I only have 12 total extras left.