I sure wish I had seen this post a few weeks ago, before I tackled a similar coupler issue. We were on the road 25 miles into a one-way trip across the country when my coupler jumped off the ball on I-78.
There was no shoulder to pull over on, so the coupler dragged on the pavement, nested on the too-loose safety chains for a hundred yards, before I could safely stop. It looked then like no way we could continue safely. The cup was mauled. I was able to nurse us to a Home Depot where I bought a length of heavy braided steel cable and cable clamps, and wrapped this snugly around the grinded up coupler. Re-spliced the wiring, and decided to give it a go.
When driving over some bridge seams, this jackass emergency solution held, (Holy Moley!), so decided there was no turning back, and we made it to NM with some sweating but without further issues.
Now the repairs:
After considerable thought, doubt and fear I finally had a plan. Cut off the bad coupler. Bought a new, 2-inch coupler. At a junkyard, got 3/16th thick sheet steel, which I then cut two matching triangle pieces to use like a "sandwich" around that angled tongue. Welded first piece to the coupler, then welded that
to the underside of Scamp
tongue. I welded the second triangle shape to the top of the Scamp
angled tongue, as an extra precaution. Was also going to run a 1/2-inch grade 8 bolt through, like a toothpick through the sandwich, but, ain't done it yet.
However, I did brush everything with fiberglass resin and then painted it (not shown here).