EAA Witness pistols are essentially CZ75 clones that have gone on to take a slightly different path.
One of their features is interchangeable calibers. Sometimes it is as easy as switching out barrels, other times you have to get a slide/barrel/mag kit. But they are all pretty reasonable all things considered.
They offer poly versions of their standard steel pistols, and I think the poly versions will still take the conversion kits. I think .38 Super was one of their kits, but I could be mistaken.
Good luck!