I use this one and it's only $11. It's tight but fits my Go, controller, external battery, USB cord and earbuds. There's probably just enough room to fit the charger too but I don't carry it.
This case was recommended to me, and you could not possibly get a snugger fit.
Outer dimensions are listed as 8.8" L – 6" W – 4.3" H. I would't get anything smaller than that.
Edit: pics