Amazon has Embossed Solid Duvet Cover Set(Twin,Full/Queen,King)in 7 colors on sale for $11.99-$17.99 with promo code IH2NUIJT.(40% off)
Shipping is free with prime or order $25+.
After code IH2NUIJT price:
Twin size for $11.99
https://www.amazon.com/dp/B071FFFSB6/
Full/Queen size for $16.19
https://www.amazon.com/dp/B01G5CCQ76/
King size for $17.99
https://www.amazon.com/dp/B072PQWP6P/