HAND THROTTLE

Grab a rear shifter, cable and housing off an old bike or at a local bike shop.  Attach the lever to your shifter.

Route the cable through the fire wall, into engine compartment.  TJ's have a nice large rubber plug above the accelerator for all your wiring needs.

I scavenged some parts of my Mtn bike to mount to the accelerator cable bracket.  You need a piece of hardware that allows the cable to go through, while letting the housing seat into it also. The pics may help explain better.  I also bought some door strikers at the local hardware store to sandwich around the cable bracket, which allow the cable to go through and seats the plastic piece.

Here you can see the door strikers, and the metal threaded piece I scavenged off my bike.  A nut screws on from the backside, tightening the whole unit together.

Here is the other side, showing the nut and the cable coming through.

Here is a terrible pic of the cable around the accelerator post, and the hardware to keep it tight.

Here is an overview of the under hood portion.