Or better yet (and way cheaper), build your own cable.
Start with this:
http://www.ebay.com.au/itm/USB-to-TT...item27d774e8f9
Solder the correct three wires to the correct pins on one of these:
http://www.ebay.com.au/itm/DB9-male-...item3a89aa5022
That's what I did and it works fine. Can't use the synscan controller when going this route.