Try specialty electrical or lighting wholesalers. You should be able to find these in your phone book, but you may have to find a "business to business" phone book to get a list of all of them. There are stores that specialize in selling to the trades (plumbing, roofing, etc.) that will sell to the public but do not make a point of advertising to the public as they don't want to antagonize their main customer base, which is the contractors. When you go to these stores, be prepared to wait at the counter while the clerk takes care of his repetitive customer who knows exactly what he wants.