If you're interested in doing it yourself, total cost for parts is about $50.00. You end up with a fully functioning throttle, just like it was still attached to the stick. It just identifies itself to windows differently.
You'll need one of these -
http://www.lbodnar.dsl.pipex.com/joystick/, a small PC board from Radio Shack (I use 1/2 of a dual IC board), 2 IN914/4148 Diodes, a soldering iron, solder and a glue gun.
I'll post instructional photos when I do the second one I have. Because this one was an experiment, it isn't pretty inside, but it works. I'll be making it look better the second time around.
I should be able to post the schematics in a day or two. I just need to put my notes into schematic form.
If you just want to exchange your throttle with the one I'm doing, and so long as the throttle you have is functional we can work something out.