Where can I find a safe and affordable waterproof mattress pad?
Here's a mattress pad with no polyester--only polyethylene and natural fibers. I don't know if it's in your price range, but they do exist.
If you can't afford this, you can get polyethylene sheeting (like a "poly" tarp sold at outdoor stores for camping) and put it on the bed to protect the mattress.
Polylaminate is a sheet of polyethylene film laminated between two sheets of aluminium foil.
This answer was provided by our friend, Debra Lynn Dadd. Hailed as "The Queen of Green" by the New York Times, Debra Lynn Dadd has been a pioneering consumer advocate since 1982, specializing in products and lifestyle choices that are safer for human health and the environment. She is the author of Home Safe Home.