Try to find a bag with hydration, 100oz will do. Molle systems is best for adaptation to your needs.
I have a first line bike bag with 70oz hydrator, packed with foil tuna and turkey packs, power bars, Emergency's, granolas bars, and three days of meds, The second compartment contains a two man space blanket, poncho, glass break hammer with screwdrivers inside, soap,a rag, campers T/P, a mirror, a magnifying glass, a lighter, and a magnesium fire stick, latex gloves, wrap around glasses, a radio, and binoculars and compass. It has and small med kit also. 30 lbs loaded. Dust masks, Wide brim hat, two gallons pf water, and extra boots and a set of clothes in my Jeep.
Security options, 3.5 ' Gerber Gator, whistle, tactical day planner with .45.
Tactical shotgun and 20 shells under fold down seats.
A have a second line 3 day assault pack with Molle for a five day pack, more heavily equipped at 45 lbs, with out ammo. Water, shelter, food, fire, and protection