kjg: the 7.62x25 can be converted to the 38 Super. Some use the 9x23 case, as a rimless version of the 38 Super, for thier reloads. I would not fire the 9x23 Winchester cartridge in my Tok - it is too hot and locks the slide back.
Toks used to come with either a 9mm or 38 Super barrel for interchange. All you have to do is remove the 7.62 bbl and spring and insert the 38 Super and springs that come with it. No change in springs for going from 7.62 to 9mm. My Tok handled factory 38 Super loads just fine, although they hit about 6" high at 25 yds. When I started shooting some of my hotter reloads in 38 Super, the slide would lock back.
I would try Kangs, in Ky. Or Sarco or Samco or one of the other large parts dealers for the 38 Super barrel.
If you want to do the conversion but can't find a barrel, get a 9mm barrel and have a gunsmith rechamber it to 9x23 - just use the barass though, the loads are too high pressured for the Tok. HTH. Mikey.