With orders of $25 or more, Amazon offers Prime members its AmazonBasics 11" Felt Laptop Sleeve in Light Grey for $1.67 with free shipping. That's $8 off list and the lowest price we could find. It fits 11" laptops and has space for a 7" tablet.

Note that this item is part of Amazon's "Add-on program" and can only be purchased with an order of $25 or more.

Update: The price has increased to $2.50.