Probably the easiest way is to buy an old CAB1 remote and Powermaster. You can find them used on ebay for under $50 each.
(I will probably have mine up for sale soon)
If you want to do the DIY route, you would have to completely disassemble your CW80 (not recommended).
But if you did, you could remove the throttle control lever and the potentiometer that the lever is attached to. Extend the wires from the pot to whatever length you like to make your tether. Mount the pot and lever in a small box and now you would have a walk-a-round tethered throttle for your layout. It would be throttle only with no bell or whistle control.