Firstly, if you're not either a 1x fan, or a lover of homebrew/diy/ghetto mechanics I'd look away now. Nothing about this solution is elegant or finely crafted, how ever it took about an hour of tinkering and cost me nothing so why not...
step one - take an old 42t chain ring and an old sprocket of the right size to line up with the chainring bolt holes
step two - drill 2 holes 10mm in the sprocket and grind the teeth off.
step three - bolt them together with chain ring bolts
step four - add it to your 11-36t cassette, removing the 17t ring (as with the one-up version)
step five - add a link to the chain
step six - turn your B- screw right out
step seven - go ride
ok it took a bit of grinding and tweaking to get the spacing right (just grinding the chainring and trying it, then repeating till it was right) the old sprocket was a 32t from some random old cassette left in my junk box, the rest was XT
so far it seems to work with no problems, but only on a quick ride, shifting is fine (with a Zee FR short mech). To be honest it seems too easy so I'm sure something won't work long term but I'll see how it goes.