If you have an old pc joypad laying around you could take the board out of that and wire up each switch in the amiga joystick to a contact on the pc joypad. So for example when you press up on the amiga stick, it will connect together two contacts on the pc joypad and send the button press through to the pc.
I did a similar thing with a megadrive pad, wired up a pc joypad board to a 9-pin socket and then plugged the megadrive pad into it, works great
