You are looking for a duvet cover? I would suggest 100% cotton, and measure to make sure the sizes match. For some reason, duvets and duvet cover sizes are not standard.

I've had success using Overstock and ebay to find the exact size I'm looking for.

Can anyone recomend a very soft queen duvet brand? We have a down comforter that we need to cover. Duvets are expensive and we want to make sure it's super soft. Any suggestions would be great! Thx