I picked up one of these at Salvation Army this weekend. It works in combination with a custom PC to 5200 adapter I had made. I tried it out with Pac Man, River Raid and Boulder Dash. The analog thumb stick offered tight control on all three games. Too bad nothing like this released with the console back in 1982.
http://www.ebay.com/itm/NIB-MAKOPAD-PC-GAMEPAD-JOYSTICK-COMPUTER-INTERACT-SV-234-/111171146455?pt=US_Video_Game_Controllers&hash=item19e25112d7
http://www.ebay.com/itm/NIB-MAKOPAD-PC-GAMEPAD-JOYSTICK-COMPUTER-INTERACT-SV-234-/111171146455?pt=US_Video_Game_Controllers&hash=item19e25112d7