It's not quite what you're asking for, but I looked into something like that for a while and didn't really find any I liked and wanted to carry around with me,

It's not quite what you're asking for, but I looked into something like that for a while and didn't really find any I liked and wanted to carry around with me, so I ended up just installing retroarch on my phone and bringing along an 8bitdo sn30 controller. I don't have a high end phone or anything but it's capable of playing everything up to the DS pretty well. I even got metroid prime to boot up on dolphin...though the framerate was far too low to play. The sn30's pretty light and easy to carry around and feels pretty darn close to an actual snes controller. Battery life's pretty decent too.