I am new to this group so I am not sure about how to do stuff on here so bear with me.
Find an arcade game or PC joystick that has enough buttons to do what you want it to do, dis assemble the joystick, isolate the different switching circuits, solder new leads, route thru to a relay board, wrap the stickshift lever with blue painter's tape,bondo the shaft of the stickshift to one half of the joystick case, pull stickshift lever free and re do on the other joystick handle. The relay board allows the small circuit capacity of the joystick to operate higher circuit loads.
Joy sticks will handle 1 amp max load thru their contacts.
Step 1: Choosing a Joystick
Try to find one that suits your fancy but doesn't cost you your first born.
Step 2: Disassembly
Most controllers use momentary contact switches in the form of lever actuated or rubber button topped. The lever actuated switches generally have 2 functions normally open contacts and normally closed contacts. Button switches only close. Isolate these switches and you have your controls. Some Joysticks have built in rapid fire circuits that open and close very quickly for arcade games. If you scratch off the copper printed board from the switches, you remove these rapid fire functions and are just using the switch.
Step 3: Prepping for Install
These can be made using Radio shack parts or purchased already made off ebay. The price and time to make one is far more than a prefabbed one. The isolation relay board generally will have a power source and 4 switched relays. The contacts for these relays are - common, normally open and normally closed. You will be energizing these relays to operate a function so you would connect a lead to power the device on the normally open contact and a fused power lead to the relay to be switched. These prefabbed isolation relays usually have under 10 amp capacity so if you are powering anything heavier you will need an additional isolation relay with higher capacity- - purchased thru Radio Shack- 3.85, purchased in quantity of 10 thru ebay 1.85 ea.
run the control wire 6 conductor thru the base of the knob by drilling a1/4 inch hole at the bottom. Insert a 1/4 in diameter plastict tube thru that hole and run your control wire thru the tube. Tie in the switching leads and power supply. Now on to the final step.
mix up a little bondo, 2 golf ball sizes, add the hardener1 inch long to each golf ball size and add to the handle and push in around plastic tube add only enough to bring it almost up to the half edge. do not let the bondo cover anything you want to have access to like switches, wires, etc. Let the bondo cure. Do the same thing with the other half of the handle, cover the seam with painters tape and fill to seam with bondo. Take the cap side of the handle and put a small baggie over the bondo as you put both halves of the handle in position on the stick shift lever let cure in place by using painters tape. Once the bondo cures, take the two halves apart and install all the circuit boards switches and springs and mount to the shift lever- there you go!. If you ahve any questions contact me at my handle @chartermi.net or leave me a message here. Enjoy explaining how you got a joystick in your car. I had a friend do this and he hooked up the trigger to a sound effects module and it made machine gun fire come out of his radio speakers. If a car cut him off- he pulled the trigger and the machine gun fire was startling . Have fun...........