I buy some stuff called PB2. It's basically a big jar of dehydrated peanuts, so it's lightweight. You just add water (or some people add vegetable oil) to it, and it tastes just like regular peanut butter. Thirty tablespoons worth of it only weighs 6 ounces. They also make a peanut butter and chocolate version. you could leave it in the plastic jar, or put it, dry, in a ziploc. I get it at (gasp, the horror!) Wal-Mart, on the peanut butter aisle.