yeoman
Actually that really is not that difficult...
What rifle, how old is it, what caliber is the bore, and what size bullet do you want to shoot (44 cal or 45 cal)? What brand/make sabots do you have now that are not working... have you ever had any that did work well for you.
I can give you a good idea - you would not believe the size of my sabot collection...
The ultimate answer might lie with Connie at MMP Sabots she catalogs what sabot fits what rifle with bullet for each of their sabots...
I can even send you a sample of different kinds and sizes, I have done that in the past on a few occasions... Lot of people are not located near a place they can run down town and get a sample..