There were Parallel port adaptors but none for the joystick port, even less the USB port.
Well, the Competition Pro joysticks that were sold for PC were normal Atari-type joysticks bundled in with an adapter for the PC joystick port. Probably you want to score one of these!
Alternatively, you can buy the Catweasel Mk3 card, and besides having two (or one? I forgot) atari-type joystick ports, you can have a real SID chip for listening to sidmusic, and you have a helluva disk controller that will read most any shit you throw at it.