Sleeve for rMBP

I'm looking for a cheap sleeve to carry my 2015 rMBP 13in around. I've been looking at the Amazon Basics one, but I'm worried it might be too big. I don't want my MBP to be flailing around when I'm running late to class or something.

For those who own the sleeve, what have been your experiences. Or can anyone suggest me a cheap sleeve that fits a 13in rMBP? Thanks