My Dad used to make them with the stones he cut or tumbled. They seemed to sell well to his buyers.
I still have one of his earliest efforts from the 60s. He made it will a braided leather string of tan and black with customary silver end pieces, then affixed a tumbled pale, milky, periwinkle blue stone (obviously not turquoise but I’m not sure what it is) to a silver cast slide of a horse and cowboy jumping over it. I would have been aged single digits, so I’m sure it’s an inexpensive piece.
He lives in Arizona now and continues cutting and selling stones at age 93. If he’s still making bolo ties, I’d guess they sell well there.