Dorothy,
I'm pretty sure it is fabric.com that has waterproof forms -so they pillows won't get yucky and mildewy over time.

bestyears, thanks I found 16x16 poly fill they say is indoor/outdoor. Is this what you had in mind that would prevent mildew and getting yucky?

Hi again Dorothy,
I was mistaken... it was this place (see link). The covers on them are waterproof. Haven't had personal experience with them, but I plan to try them very soon.

Here is a link that might be useful: Waterproof pillow inserts

I made seat cushions and pillows for my iron peacock chairs. They get wet and they smell fine and dry at the same rate as the cushions I've purchased for the other decks. I used upholstery foam for the cushions(nothing special, it's low density...high porousity) and polyfill for the pillows.