Washable Spin Bike Cover?

I am looking for recommendations for a washable / removable spin bike cover.

We have an SB2 spin bike with a comfortable seat, but the seat is not removable / washable, and a few gallons of sweat each week make it stanky!

So I don't want a full seat, just picturing something that slips over the top / drawstring, that can be removed and washed weekly. Thanks!