Mine were added to a tractor that the dealer had in stock, so I had the option to use the joystick placed where I could reach it from behind the tractor. That wasn't my idea, but was suggested by the shop foreman, and it's been much more user friendly than using the factory solution levers to the right of the seat. I don't remember what the cost was, but you can get an idea by searching the forums. Probably about a grand or a little less.
I believe they're standard equipment with the 6530 that clydes has, but reaching the controls through the back window on the cab might be a trick! /forums/images/graemlins/mad.gif