There certainly are
. It's called a luggage sleeve
. Go and check out Lowepro's website, I'd say
I'll mention each series of which I know at least some models have this feature and which bags exactly have it
Nova AW series:
Classified AW series:Magnum AW series:CompuDay Photo series:
SSM/NEX-5/18-55 OSS/Lowepro Pro Trekker 600 AW/CompuTrekker AW/Nova 140 AW/Street & Field gear/Toploader Pro 75 AW. And a huge wishlist...My photos on Flickr...