Why don't you just look for the factories that do the plastic moulding? Look some of them up in the business directories or yellow pages and call them up -see whether they can mould them for you and if they have made/are making them. You'll definitely get your plastic boxes cheaper than from Home Depot and the like, but the factories will usually take a minimum order of, say, 1000 units. You have to serious about your business endeavour (making WC kits) and be sure of a receptive market for your product before taking such a plunge...LOL