This link new Useful Stuff page now links to a number of products people mention at bedbugger.com. There are links to purchasing mattress covers, ziploc XL bags, food grade DE, and so on. This was recommended by a reader, and I hope it helps you.

As many readers know, many of us use National Allergy mattress encasements on our mattresses (and box springs, if we have them), and I am one of those. After many Bedbuggers had been using and recommending the encasements on this site for a long time, National Allergy offered Bedbugger readers a discount on all [...]

We’ve been recommending National Allergy covers since we started the blog, since a lot of readers have been happy with them.
I personally used two vinyl covers from Target for $10 each, which each ripped in turn. Then I got a National Allergy one. I like this one because instead of the [...]