A new thread would probably get better responses.

The 4” barrel was the standard for .38 Special. Gunpartscorp.com has both the .38 Special and .38 S&W barrels for sale in their appropriate lengths.

However, lik Muley Gil mentioned I’d be surprised to find a shot out .38 Special barrel. Unless someone was loading up some corrosive ammo and not cleaning afterwards, you’d have to do some serious shooting to wear out a barrel.