I think you will be out of luck as far as celtic studs go. I have been searching myself and studs tend to be either much of a muchness (usually black onyx) or very expensive solid silver (usually black onyx)

K J Beckett at http://www.kjbeckett.com/acatalog/shirtstuds.html has some interesting designs and Silver Groves at http://www.silvergroves.co.uk/ecomme...hirt~Studs.htm has some nice upmarket studs but none of them are celtic