Computer pocket is too big for MacBook Pro

Hello all--

I have a backpack case that I would like to use with my MacBook Pro, but the computer pocket is designed for a PC laptop and is so wide that I can't "strap down" my mac - the velcro straps stretch too far. I thought I'd try putting the mac in a sleeve and then in the backpack. Can anyone recommend a good padded sleeve for this purpose? I'm trying to research this but there are just too many products on the market.

Thanks.