Most any local sheet metal fabricator will carry aluminum up .063 (1/16th of an inch) in sheets. You can also get variety of thicknesses from Shapiro Metal Supply, Online Metals, ASAP, and The Metals Depot. they all ship small quantities to rsidential addresses and will cut pieces to size for a minimal charge.

I don't know what kind of adhesive but the metal would need to be spotlessly clean. First use an automotive grade wax remover on the metal and then some metal prep cleaner, both sold at body shop suppliers. The cleaner is designed to not leave any deposits on the metal that you might get with soap and water, alcohol, lighter fluid etc. It is what I use before powder coating camera parts.