I just get a length of 2" angle aluminum stock from Home Depot and cut it into 6" lengths or whatever width your vice jaws happen to be. I like to get the 1/8" thick pieces. If they stock 3/16' that would be even better. Lowes might have a better selection of thickness.
I've found that putting the magnets on the squeeze side destroys the magnets pretty quick, so I epoxy them to the side that goes against the top of the vise. They tend to wiggle around a bit when the clamping presssure is applied, but snap back as soon as the clamping pressure is released. Saves the magnets from getting crushed.
Something like this:
https://www.homedepot.com/p/Everbil...inum-Angle-with-1-8-in-Thick-801407/204273991
This 36" piece would yield 3 set of 6" jaws for less than $15.00
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