There are a couple of good brands for aluminium (aluminum, to our US friends) panniers, like Metal Mule, Touratech, Hepco and Becker, etc. Most of these have online shops, or local distributors. Their websites should be able to help you. I ended up getting my panniers custom made by a guy in Guernsey (thanks Jim!). The more tricky part might actually be finding pannier racks that fit your specific bike. What do you ride? I got my racks (for KLR650C) from Hepco and Becker in the end (I still haven't installed them.. trying to find time in daylight). For the mounting kit, a lot of people use the Touratech mounting kit, which is one of the better options. Seach for "mount kit" or "mounting kit" on the touratech website for details.
There are plenty of references in the hubb to aluminium panniers.. take a look at the HUBB search facility.