Materials cost about $25 at Home Depot. The shock cord cleets and cavities made perfect foundations. Unscrew them and press a 1/2" copper plumbing or aluminum tube into the cleet and cut off what sticks out. It fits snug. Next press a 5/16" coupling nut into the 1/2" tube and it also fits snug! Drill a hole(about 1/2" dia.)through the bottom of the female cavity and screw the cleet back in.
The handles are 18"x3/4" square aluminum hollow rods. I threaded 3-1/2"long(full length thread) x 5/16" carriage bolts through the handles...through a lock washer/nut/larger washer. Then continued through the 5/16" coupling nut...through the hole in the bottom of the cavity...and finally used a large washer w/lock washer and another coupling or wing nut as shown.
The trick is to tighten/tweek it all so that the square part of the carriage bolt bites into the handle. Also... the bolt extending down near the steering handle hardware will need to be shortened so it doesnt interfere. All in all - I`m very happy with the results. It was easy to do & it feels solid/secure while providing a nice grip.