I’ve been using a sleeve that I bought for my 11" MacBook Air in 2011 (and for it’s 2015 replacement). I not have a new 13" MacBook Air and it doesn’t quite fit in the old sleeve.
I think the old sleeve is labeled “Cobac Sac”, though it’s hard to read. It’s got burlap on the outside and fleece on the inside. I can’t find any mention of it on Google.
Does anyone make something like it today that would fit the new Air?
You don’t say much about your preferred aesthetic, but based on the burlap exterior of your current sleeve, I’m going to guess that an outdoors or rustic vibe is OK with you. So, have a look at this sleeve:
I have lots of Topo gear, both apparel and bags, because their products are well designed, well made, and have a lifetime warranty.