It seems like hot stamping is dying out. CPC is the only custom clay MFG left. They will do it, but it ends up being close to the price of labeled chips.
TR King was a great place to get hot stamps from. When I got into the hobby around year 2000, you could get hot stamp solids for .50 cents each. Back then many turned up their noses at TR King because they are not quite 39mm. They were popular for a few years, but not enough to keep them in business.