mask cover; face mask cover
A cloth or disposable cover worn over a face mask, often for decoration, extra protection, or to extend the life of the mask.
When you put on a mask cover, a regular mask looks a bit more stylish.
During hay fever season, I wear a mask cover over my mask as a countermeasure.
Variant with a middle dot; less common in everyday writing.
Wasei-eigo (Japanese-made English) from マスク (mask) + カバー (cover).