Does anyone make a plastic sabot for using .490 round balls in a .50 rifle? If not, does anyone make sabots for using some other size round ball in a .50 cal. rifle?

My rifle is a T/C Hawken I built and modified 40 years ago. The barrel is a custom with .500 bore, .511 groove, and 1:75" twist with wide grooves and narrow lands. It's been mothballed for 35 years. I used it with .490 swaged balls, .015" Ox-Yoke strip patches soaked in melted Crisco and cut flush with the muzzle after starting the ball. I used 90 grains of Goex FFg and a Remington #11 cap.

I plan to convert to a 209 primer nipple and use Blackhorn 209 powder.

I would like to try plastic sobots with lead round balls. I have always used .490 balls, but to try sabots I would try to find whatever size balls that the sabot required.