Not a backpack, but I personally use this to bring my setup to school, etc. It easily fits the NFC S4 Classic Mini along with power adapters.
In my use case, I've managed to fit a 15.6 portable (DIY) monitor,mouse, as well as two Xbox one controllers (which are inside individual hard cases).... Keyboards are a tricky issue though. I assume a tenkeyless would work fine, but any full-size is out of the question. Although, if I wanted to bring something the thickness/size of a Cooler Master MasterKeys Pro S then I would have to omit my portable display. Something like a compact bluetooth keyboard fits fine in either condition....
For the most part, biggest selling point for me was the ability to roll the bag if I need to since, during my daily routine, I end up walking a decent deal away from parking lots and in/out/around campus which, coupled with the overall carrying weight, makes the bag tiresome to carry by hand (especially if you happen to have other bags/backpacks/equipment with you). When I'm not rolling it, the handle can be completely hidden as well.
- I can probably try to post a few images if you happen to need them.
https://www.amazon.com/gp/product/B00VIM9VQ8/?tag=theminutiae-20