We have some small pendants and chain tabs at Rings & Things that can be engraved. You can see them at http://snipurl.com/1rf2r We can have some of the designs laser engraved with your design or logo if you are wanting them for logo tags next to your clasp. Minimums are much lower for laser engraved tags that for more traditional custom stamped tags. Contact us directly (1-800-366-2156) if you are interested in the laser engraving option.
Other places I know of for custom stamps and stampable tags include
Harper (www.harpermfg.com)
Microstamp www.microstampusa.com
www.infinitystamps.com
and possibly www.thunderbirdsupply.com