Well.. if you're looking for something really specific and don't mind overpaying... search for "custom collar" in Google or whatever and there are a number of different sites that will allow you to design a collar to your specifications.
But really... just go to a pet store. Pet stores have a wide variety of sizes of collars, with and without spikes, and in a number of colours. It's cheaper than ordering one, and you'll end up with pretty much the exact same thing. Plus, they usually carry the matching leashes, if you do end up wanting one of those too. Any pet store will do.