Hi forthemame,
I went through and fixed most of the links in the protector post here and in this post that it links to. Some of them changed the URL on their websites so the links were broken and I hadn’t checked them in a while. Thanks for mentioning it (hopefully I got all of them).
Most of the thin membrane types of protectors are very similar products with a similar membrane and all of them have their share of complaints about the membrane failing in some cases but I suspect that many of them are from not following the care instructions because heat can degrade or melt the membrane. The biggest difference between them is in the fabric layers that the membrane is bonded to.
While many of them only have the waterproof membrane on the top surface … there are also some that protect the top and all 4 borders of the mattress. I would look for wording that says “5 sided protection” or “protects the top and sides” or something similar that makes it clear that they have waterproof protection on 5 sides of the mattress. A few manufacturers that make these that showed up with a search include …
https://www.maloufsleep.com/products/sleep-tite-protectors/
http://www.purecare.com/shop/c-1-mattress-protection.aspx
http://glideaway.com/products/protectors/
Phoenix