The places I've seen who do it are at the big shows. I don't remember any of their names at the moment but maybe just keep an eye out and ask at the big shows in your area.
But one thing I want to say is what are you showing in? If you are or will ever do anything other than jumpers then skip the crystals. I can't remember if the rule passed or not to make the bling-ed helmets illegal or not but at the very least they are quite frowned upon by judges.