As a Buck rider myself, I've got contacts for a guy in Germany that has some originals. I bought a set last year.
Gil is great and he's done some Buck decals for a chap in the UK recently.
Also, there's a couple of eBay sellers who've started putting up quite a lot of replica decals. Only seen Ti, Yo and Shock a Billy and can't vouch for quality bit might be worth a look. Check completed listings for contacts.