I have a mesh Jansport backpack that I've been using since 1996. It's just a simple school backpack, single big compartment and a single outside pocket, it's just made out of mesh. It's still going strong. If the only thing you put in it is those water bottles I think it would fit. I always ride with mine, although I carry food and gear in the big compartment and tools in the outer pocket. Total weight 12.6 pounds.
I see several on search. No guarantee they're still bombproof.
https://duckduckgo.com/?q=mesh+jansport+backpack&t=ffsb