Small tablet or phone that runs Kali without problems?

As part of my job I sometimes need to demonstrate that a certain wep network is actually vulnerable (sounds stupid, I know...).
Well, until now I always carried a whole notebook with me that could run Kali, but I would really prefer a device that fits in my pocket.
Can anyone of you suggest me a phone or tablet on which I could install Kali without too many issues? Preferably one that could make use of my external wifi adapter (Alfa AWUS036H). I only know very little about Linux and I don't want to spend hours on solving problems and getting driers to work etc. I also don't want to run Kali in a VM or something like this.

Best regards,
Nopme

You should have a look at Nethunter, which is a Kali chroot environment plus a couple of apps for Android, which works for most Nexus and Oneplus devices. This solution is most probably easier and more comfortable than installing Linux... and you still can use your phone as a phone. ;)

I have it installed on a 2013 Nexus 7 and it works like a charm.