Ohio Ordnance appears to be out of SG-43 barrels. I would rebuild the deactivated original barrel using a whole Moison-Nagant rifle barrel as an insert into a bored-out SG-43. The Red Chinese did this trick to convert many MG barrels after WW-II.
It would be well to tap and cork up the drilled holes (use permanent Loctite...) before boring the barrel for the insert. The insert must be thick wall to contain the pressure unlike the usual barrel liners which are paper thin.
The SG-43 barrel is bored out on a decent-sized lathe using a pilot nose drill bit of appropriate size with and extension silver-soldered on to reach the length.