See this link for building a custom VX-8 cable: http://users.tpg.com.au/vk4go1/vx8-2.htm
Note: you can buy just the connector with a cable on it for the VX-8 from RT Systems for $8. You still need something to get 0-3.3V.
If you have multiple radios I would get one FTDI serial adapter and wire different ends. You could use the 6 pin FTDI cable.
See TTL-232R-3V3 or TTL-232R-5V depending on whether you need 3.3V or 5V.
http://www.ftdichip.com/Products/Cables/USBTTLSerial.htm http://www.ftdichip.com/Support/Documents/DataSheets/Cables/DS_TTL-232R_CABL...
You can get that cable as well as some other good FTDI usb serial breakout boards from some of the electronics DIY places like Adafruit, Sparkfun, Seeedstudio, etc.
https://www.adafruit.com/products/70
Or
https://www.adafruit.com/products/284
Or
http://www.sparkfun.com/products/9873
If you are doing other things with micro-controllers, wireless router hacking, you will probably wind up with a few of these in your toolbox anyway as many embedded devices have a 3.3V or 5V serial console buried in there somewhere.