You can buy transmitter -> parallel/serial/USB cables from various places, but they won't be guaranteed to work with the simulator that you're using, as the manufacturer's replacement would be. I agree with Charlie -- call or write the mfr. and see if they will sell you a replacement cable.

If they don't, you can try one of the adaptor cables from http://www.milehighwings.com/ they have quite a good selection. Try to get the one closest to what you are replacing, and maybe it'll work. Not sure whether your cable is USB or not, but if it is, right now they are out of stock of USB cables, supposedly 8-10 days lead time.

Good luck.