I guess you mean the FMS free simulator.

If it has to be the joystick port then the electronics required are quite complicated. You can buy a joystick interface that simply plugs into the trainer/buddy socket though you'll need to make sure that you tell whoever you get it from exactly which model of Sanwa Tx you have. The older ones e.g. VG series and the newer RD6000s have completely different trainer sockets.

Try http://www.rc-electronics.co.uk/ I know Ken does a good job and his prices are very reasonable. There are others around too.

There are also other interace types which connect to the parallel/printer port or the serial/COM port. These are simpler so cheaper or easier to build but they don't work with Win 2000 or XP.

Steve