UPDATE: 4/10/24 to give more tolerance for magnets.
Here is a set of smooth soft jaws I made. I made a set for each vise I use daily. 2.5" Yost, 3" Yost, and a 4" Morgan Chicago 40. They are sturdy and hold up well at least so far. As a knife maker, I often find myself looking for something to hold work without marring it.
Each set has a recess for magnets. The 2.5" and 3" take 8x3 mm magnets and the 4" takes 12x3" magnets. All can be found at local craft or department stores as well as Amazon. I left the recessed areas a tight fit on purpose. I did not want to rely on glue. I heated the holes with a lighter and then pressed them in with my fingers. Finished pushing them immediately in the vise. Worked great!
I printed these on an Ender 3 V3 KE with the following settings.
Be sure to check my other things. I have a knurled set and a V grip set coming as well.