With a separate compartment for shoes and gadgets, plus a USB charging port, this bag is certainly your best bet for hauling over a month’s worth of supplies across international waters.
Promising review: “THIS BAG DOES EVERYTHING! FITS UNDER PLANE SEATS and HOLDS A TON! I relied on previous positive reviews before purchasing this backpack, and waited until I just finished my own 2-week international travel to write this review. There are compartments everywhere, including one at the low back that perfectly securely and safely fits your passports and travel docs, one underneath for shoes or wet items, three large sections [with smaller additional storage compartments inside] that I used for laptops/iPads, large makeup bags, and a change of clothes, plus a small outside zippered compartment for those small items you want to reach quickly [ie: hand sanitizer medicine, etc]. The straps are comfortable and I walked through numerous airports, hotels, train stations, and more without any pressure on my shoulders or back.” —Beach and Mountain Lover
Get it from Amazon for $29.99+ (available in 43 colors and two sizes).