If you want cheap look locally, delivery charges on materials are ridiculous nowadays. Just look up local stock material shops in your area. Try the yellow pages, under metal wholesalers or if all else fails look up local fabrication shops. Spend a bit of time on the phone telling them who you are and what you're looking for, you should be able to find someplace local that sells a variety of extruded aluminum stock. Even if you find what you're looking for try calling around to a good number of places, you may find a better deal or selection someplace else. Different companies will have different attitudes when dealing with people only purchasing small amounts so you may get the run around at a few places.