I don't know much about this ... But I'd think that a good commercial-quality Gaelic typeface, a good Irish Bunchló or Seanchló, would be a start. Some engravers might be able to transfer the font directly to the engraving, or use a printed sample as a template or model. You can Google "cló Gaelach" and follow some of the links.
Don't know if that's helpful ...
P.S. I'll copy this to our Irish Language forum, so check there for possible answers, too.
Vivat diabolus in musica! MTGuru's (old) GG Clips
/ Blackbird Clips
Joel Barish: Is there any risk of brain damage?
Dr. Mierzwiak: Well, technically speaking, the procedure is