Where can I get a Berkshire Sablesoft or Serasoft duvet cover for a queen bed?

I’d prefer to find it in a beige or dark brown, but have googled everywhere and have had no luck

I’ve found a lot of good bed sets and duvet covers here: http://www.duvetscomfortersandbedding.com/.

Also, try looking at Bed, Bath and Beyond. They have some good quality products in brown there.

Good luck!