GiGi,
I bought(many years ago, before I got RA...just had weak hands) a jar opener that is metal. It has 2 "claws" at the front and on the handle theres holes where you can select the size of jar you need to open. Its really handy for me, especially now. My grandad had one of those rubber pulley things that Ducky described and he swore by it. He got his at Wal-mart, or Canadian tire. I'm not sure.
Good Luck. Hope you find what you need.