Looking for something else, I came across silicone seals for canning jars, where the silicone replaces the metal + rubberized lid, but not the band. They're all reusable. Some might be BPA free.
I've never done any canning, but I keep thinking I should try it. I have a lot of canning jars which I use for other storage.
Are these a good idea for canning? Any caveats?