Just a thought, but how about coil trim aluminum, the stuff siders and roofers bend for drip edge, fascia and rake trim. It's thin enough and possibly could be bent around a piece of pipe, you just wouldn't have end caps. Paint to match or contrast.
Was thinking about having a guy i know down here in FL look at it.
He does a lot of baat canvas tops and has all that sew on strap stuff for valcro
I notice there is a nice lip under the molding that covers the top of tail gate, that molding is also broke.