My wife has an etsy shop, but doesn't have sleeves up on it as she does mainly things for little kids like headbands, scarves, etc.
She made a wool felt sleeve similar to
this for our MBA, Surface RT with touchcover, and my moms Dell XPS 12. She made them because I asked her and didn't want to pay the $30-$80 some were asking lol
If you have any interest in something like the above, send her a note
Unique handmade accessories for children by OhTinyGifts on Etsy and ask her for the WPC discount and I will make sure you get a good price
There are also different colors of wool felt or certain other materials that if you like let her know and she can see what she can find.
Just a thought, not necessarily trying to promote her site, just an option that may be cheaper than some others and give you a unique sleeve.