Have you tried looking in an upholstry shop or a craft store for the foam.

I think quilt batting would work as well. Really you only want something soft to cushion against the parts being tumbled around.

I've cut up an old blue high density foam sleeping pad for projects such as yours, Lisa. Look in the camping departments in Target, WalMart, etc.

Try this link for your foam.
Kathy G in MI

Here is a link that might be useful: The Foam Factory

Thanks for the ideas! I did get a foam mat at walmart, I was looking in the wrong area of the store the first time.

I used an old 3 dollar lol, lunch box. It was 5X7 or bigger , cut it and put fabric around it. Then I used Velcro on all the ends so I can change it up from purse to purse as a change it. Also maybe use and cheap exercise pad you can get at walmart for 6 bucks because then you can make a few diff ones for cheap.