Welcome eric. I have seen a setup in a Trailblazer where it did have hand controls. Since the H3 would be close to teh same thing, I'm positive it can be done.
Go to your local HUMMER dealer and sit in a LUx package and move the seat up and forward to see if that part will work for you to start. If it does, the hand control part should be easy to do.
Here's one I found that could work. Your dealer shoudl ahve some better resources though.
http://http://www.advanced-mobility.com/Products5.htm