First problem in your quest. One piece grips are "fit" to the gun at the time of manufacture. After fitting, the frame is finished. USFA is now DO DO so you don't have the option of sending it back to USFA for grip fitting and re-finish.
After-Market grips (one piece) are "built up." Three pieces are involved, right and left grip panels and a center spacer. After fitting the grip panels and the spacer to the frame, everything is glued together, than disassembled, final sanded and finished.
Start with a Google search of Grip makers. Find someone whose stuff you like and start correspondence. Best of Luck.
Coffinmaker