This is the exact dimensions of a hockey puck, with the material being aluminum. Additionally there is a center hole for a bolt and a recess for the bolt head. Each side of the puck has a 1" diameter recess so that you can assembly the stack with a spacer, which gives the stack more sideways strength rather than just relying on the bolt.
Two versions are available - for a 1/2" bolt and M12 bolt.
CAD
Metric (M12 bolt) version Solidworks DWG STEP
Inch (1/2" bolt) version Solidworks DWG STEP
Hardware
Bolt M12-1.25x70mm flanged (head might need to be ground down)
https://www.amazon.com/dp/B0CCV7QC6P
Spacer 1" OD 1/2" ID 1/4" long
https://www.amazon.com/PATIKIL-Aluminum-Spacers-Standoff-Silvery/dp/B0CX1RFHWB