I managed to coax my 8" tablet turned horizontal to give me about 80x22 at a size I could actually read.
Combine that with a ~10" bluetooth keyboard that fits comfortably in my leather jacket's inside pockets and I get to leave the house without carrying a bag and still sit and write code in the back corner of a handy beer garden.
Turns out to be surprisingly productive as well, probably because there's just enough extra friction to flipping to my usual distractions compared to a laptop that I tend to just take a sip of my beer while continuing to glare at the code instead.
True! A tablet and an ext-keyboard do a much better job (Although I wrote bag.sh out of boredom while stuck in a beer-less airport waiting for a delayed flight; I hope I won't have to actively plan for this setup again)
I have a stack of Thinkpad Tablet 2 bluetooth keyboards (though it's getting a bit low, will have to find somebody on ebay or whatever that still has some again soonish) - they're capable of being paired to more than one device (I also use them with the tablet half of my Helix 2) and have a built-in stand which takes my 8" tablet just as well as it did the Tablet 2 itself back when I was using that.
So had I ended up in the same situation as you I would probably have done similar, but with an added undercurrent of "Matt, you idiot, how did you manage to forget to put the keyboard in your pocket before you left?!"
(still a neat hack on your part, mind, no question there, but I'm very much glad I've optimised by standard "leaving the house" loadout so inflicting the same thing on myself is at least *less* likely ;)