There's an extra blanket in the bottom drawer of the cupboard.

衣橱的底柜有一条备用毯。

《柯林斯英汉双解大词典》

Could I have an extra blanket?

能多要一床毯子吗？

youdao

Could you bring me an extra blanket?

请你多拿一条毛毯给我好吗？

youdao

To avoid injury the BCA advises people to take their own pillows if staying away from home and lie on an extra duvet or blanket if the mattress seems too hard.

BBC: Bank Holiday health risk