I couldn't resist, so I got the SFC30 (the European version).8Bitdo SNES30 Wireless Gamepad - these things feel pretty darned close to the real McCoy. They're Bluetooth as well and natively supported in Retroarch, so configuration is very straightforward.
(this stuff is also available on Amazon, if you prefer)
I once managed to get a huge blister on my thumb ater 30 minutes of play after going full throttle at Killer Instinct. Ah the nostalgia.