this is who i think i use to use, i'm not sure because the website has changed a lot.
www.guitardecals.co.ukone word of advice, decals are usually printing with a laser jet printer. when you get the decal. handle it very carefully. it is possible the literally knock the ink right off the paper. lay the decal down flat and spray a very very thin dry coat of clear gloss lacquer over it. use a rattle can, a gun would be too heavy in most cases. put on at least 4 coats, very thin and dry. this will prevent the ink from flaking off the decal. I have to stress the thin lacquer coats because if the decal get just a hair too wet the decal paper will shrivel and it will be ruined.
if you need any advice placing the decal, let me know. hope this helps.