I've been looking for quite a while for someone who will hot-stamp chips I supply. All those I've asked say they will not take a chance on it as the chips may be old and brittle and they don't want to be responsible for breakage during the process. I think the only practical ways are to either apply a printed sticker, or silk screen them.

The new laser engraving engine that became available for the PC recently may be an alternative, but I haven't found anyone providing the service yet. This could be a very inexpensive alternative, as there is no tooling involved, only the creating of the artwork on the computer.