I have one of these and it is great http://www.amazon.com/SS-Controller-Adapter-for-PC/dp/B0089O10BC/ref=sr_1_2?s=videogames&ie=UTF8&qid=1425810688&sr=1-2&keywords=sega+saturn+usb+adapter

For a bonus try to connect it to a PS3...it works! :)

I'm using the 2 player mayflash adapter, upc looks like( 6 902012 050414 ) and RetroArch picks it up great, analogue sensitivity tested in the Sega touring car calibration menu and it looks good, but triggers are just buttons. I got it off Amazon https://www.amazon.com/gp/aw/d/B0089O10BC?psc=1&ref=ppx_pop_mob_b_asin_title

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.

https://www.amazon.com/Mayflash-Sega-Saturn-Controller-Adapter/dp/B006ZBHXEO/ref=sr_1_1?ie=UTF8&qid=1539273874&sr=8-1&keywords=mayflash+saturn+adapter

https://www.amazon.com/Mayflash-Saturn-Controller-Adapter-Converter/dp/B0089O10BC/ref=sr_1_2?ie=UTF8&qid=1539273874&sr=8-2&keywords=mayflash+saturn+adapter

For the controllers themselves you can find ebay sellers who do a pretty honest job cleaning up and testing vintage gamepads.

https://www.amazon.com/Mayflash-Sega-Saturn-Controller-Adapter/dp/B0089O10BC

Then just use saturn controllers.