It's the pricier route, but I recommend picking up a Mayflash Saturn adapter with a vintage Saturn pad. I've heard shady things about pretty much all the unofficial clones for Saturn pads.
For the controllers themselves you can find ebay sellers who do a pretty honest job cleaning up and testing vintage gamepads.
The only experience I have is with this: http://www.amazon.com/dp/B006ZBHXEO/ref=cm_sw_r_udp_awd_nCY5sb1XWNWWV
It works fantastic for the regular pads, Windows just works with it.
However, It does NOT work with the 3D control pad though, so not for you.
One of these with a real Saturn controller: