Deacon,
Do you know the chamber diameter or the diameter on the throat where the bullet exits the Cylinder?
I ask because I believe the early .38 S&Ws had a slightly larger case diameter and bullet diameter. Plus I've read where the official default bullet weight was 158gr but sometimes I have read the standard originally was less.
And, yes there are molds available you just need to decide what diameter and bullet weight you want. If you can use it there is a pretty nice one at 140gr and you can specify the diameter you need.
https://accuratemolds.com/bullet_detail.php?bullet=36-140C And there are more.
The throat diameter (measure it) where the bullet exits the cylinder will give us a starting place to determine your needed diameter, a true major rifle bore diameter would be even better. You may need Ø.358 or you may need Ø.361 or sum'thin else. However you may get a slight "swell" with a Ø.361 bullet (probably not noticeable) but you have to use a different expander to open it up enough o accept it instead of standard .38 caliber bullet.
Measure the chamber from the rear too, it will be another clue, if it is in the Ø.379 range it will probably be a Ø.358 diameter bullet. If the chamber is Ø.385 plus then your billet will probably be Ø.361 pus. I also believe some people shoot modern .38 S&W cases in the older larger chamber and use hollow base Ø.358 bullets to assure sealing as it travels down the barrel.
~Mako