Just wanted to throw this out there in case anyone needs this info.

We bought Nova brand memory foam mattress toppers from Costco and found out that they have these gel beads suspended in the memory foam material.  These gel beads like to fall out of the foam whenever we change the sheets or have to move the mattress topper.  Then of course, if we don't get to those bits fast enough, our dog licks it up and it makes her sick 

Fleetwood makes http://www.amazon.com/Cotton-Fleetwood-Mattress-around-mattress/dp/B001M57ME4/ref=sr_1_1?ie=UTF8&qid=1340994027&sr=8-1&keywords=30+mattress+cover - 30" and 39" width (r-pod bunk width) fully-zippered cotton mattress covers, that we're currently using to help keep all that stuff in the foam where it belongs. 

The cotton material is a cheap cotton muslin but it's a ready made product that fulfills our needs.