Hi JenovaImproved:
There is a listing on the forum here were Phoenix has listed quite a few of the better mattress cover suppliers. Here is the link. You have to scroll down to the bottom of post #4 and it is listed under the heading FOR MATTRESS or TOPPER COVERS. There are links there so you’ll be able to take a look at the web sites to see if there’s anything that you like.
In case what you meant was a mattress protector (I know, the wording the industry uses is confusing 
), there is a list of good suppliers for those in post #89 here.
I hope that is helpful to you!
Jeff Scheuer
Mattress To Go