I use LPS #3 on the inside of my bike frames and am pretty happy with it. Another, that is sold for bicycle frames but I'm thinking would work, is JP Weigle Frame Saver. Sticky stuff and smells like blue cheese, though it doesn't taste like it.
The LPS you can get at a hardware store, the Frame Saver you can get online or at your local bike shop.
I like that vacuum seal idea!