Duvet cover?? I got a down spine comforter for christmas but i need a...

I got a down spine comforter for christmas but i need a duvet cover.
I found some pricey ones at target and some other at department stores but they any wouldnt match or are to expensive.
Where do you recomend i find one? Should i just achieve a plain white one cheep somewhere or could i find one that matches and isn't to expensive? thankfulness!