I will point out, for whatever it's worth, that not having a waistcoat for the PC isn't too big a deal - it's entirely proper to just wear it with a dress belt. Or, alternatively, you wear the waistcoat and not the belt. It's just a matter of whatever look you prefer.

If worst comes to worst, one of the low tuxedo vests is the same thing. You'd just need to put silver buttons on it.