Mods need to move this thread to the whiner forum. What? No WHINER forum? Guess we need a new one. Waaaaannhhh!
If you bought a true custom, then the custom maker can make you a shaft. Secondly, if the cuemaker doesn't offer to build you a matching shaft to your specs, then, you didn't really buy a custom. You said it was a sneaky pete, so if you are talking about the 'Sneakiest Pete", then you are dead wrong. Plenty of cuemakers use the 3/8-10 Acme pin or flat-faced not to be confused with 3/8-10 McDermott style.
Who made your cue?