​I'm Always here o.o just lurking in the shadows

But I'm starting to seriously look at portable digital art options and google isn't being very helpful so I turn to the masses -

What I'm looking for:
Windows

USB Ports
Fully portable, stand alone unit IE Can draw on the screen
Powerful enough for photoshop or MS5
(I'm not a layer whore and my average dimensions don't go over 5000px)

The only units I can find that are like this are Surface 2 or 3 and the Cintiq Companion.
Now price is a slight issue - I would like to stay in the 500-700 range
And this is research to present for those that would be buying for me as a gift IE my husband is very much against used electronics so that argument has to be compelling if its to save on cost.

What I would like, is either suggestions on other available units OR reviews of the above such that I can make a compelling argument as to why a used version of them isn't the devil.

Thank you guys!