https://www.amazon.com/gp/aw/d/B002BFVAV0

Will cover Sega Mega Drive 6 button controller, also has shoulder buttons for SNES and the D-pad is better for rolling actions on Street Fighter II.

Despite the mediocre reviews, this pad from Retro-Bit is awesome, and is basically identical to a Saturn pad. But yea looks like they are making officially-licensed ones for PC soon as well.