My main travel backpack is the Lowepro ProTactic 450 AW II. I love it because it's very rigid and cushioned, and I can modify it depending on the cameras I'm taking. Usually, I carry a full-frame camera, two lenses (one of them telephoto), a 360-camera, various chargers, wires, batteries, and an Asus ultrabook (14"). The laptop compartment is limited, I cant squeeze in my 15,6" gaming laptop, so make sure to check the specs on the official site. I also have a few slots left to roll several t-shirts and other bits (yes, I roll all my clothes hehe).
On the outer shell, I attach a bottle holder, tripod, and various selfie sticks (including an extendable 3m pole) via MOLLE attachments. The reasons I love it are its versatility, built-in rain cover, and detachable belt thingy, which includes several MOLLE attachments and zip pockets. I usually walk around with it when on-site, leaving the main backpack in press rooms or hotels.
Another alternative could be the Lowepro Flipside BP 400 AW III. It’s quite similar to the budget Chinese backpacks that many publishers give out as merch. I have one from Bioware that has served me well for three years, and yes, it can hold any gaming laptop.
TDLR: since you have plenty of time before the trip, i'd go with this 15$ backpack or similar alternative and see if it can hold all you need.