While we don't recommend carrying your laptop while spinning on your reining horse, if you do, you'll want protection*. Rein in My Heart from Kellie Lewis' Kick Black Collection is now available on a super sturdy and soft laptop sleeve. It's padded and double zippered for added protection for all your rough and tough needs. Comes in 13" & 15".
13" holds Macbook Air; measure corner to corner diagonally to determine your appropriate size.
*Kicky Brand doesn't actually guarantee that your laptop would survive being carried while riding a horse. That would be silly.