Thanks to all for the great info on here.
I repaired mine today, following roughly the guides given previously, but doing it slightly differently.
So lets look at the whole story. My daughter called me yesterday afternoon, to say she'd just arrived home, and when she went to park up, the Envoy got stuck in reverse. I told ther o kill the engine, and wait with the vehicle.
I consulted the forum, and my search brought me to this thread. I read, inwardly digested, then went down to my garage and got some safety wire, and pliers. Twenty minutes later, a temporary repair was in place, and the vehicle was drivable again, by the simple expedient of locking the cable end on with wire. It worked, but wasn't exactly smooth going in and out of park.
So today at work I got to thinking about it, and figured it would be better just to have a nut and bolt to hold it on. So when I got home, I inspected my stock, and liberated a couple of 10-32 bolts, some washers, nyloc nuts, and a couple of inches of 5/16" grease line (Sometimes it's good to be a field Service guy, you keep all sorts of items "just in case").
Once I got the Envoy at my garage, jacked and on axle-stands, I got under and cut the wire I'd previously fitted. Next I removed the remainder of the original grommet, inserted the grease line, and marked it for length (width of the cable end +1/8"), and cut it.
Then I removed the shift lever, and not having a grinder handy, but a convenient drill, I drilled out the original pin.
Next I put the bolt (with a flat washer) through the shift lever, fitted the grease line, another flat washer, and a nyloc on until it was two threads of being fully tight. I then cut the bolt to exact length.
After that it was just disassemble what I had, put the shift lever back on,place the grease line in the grommet space in the cable end, then align, push the bolt through, washer on, and a fresh nyloc to secure.
You could use any low friction stiff tubing you wanted, as long as it fits the grommet hole. Just make sure you leave it a little long to prevent pinching when you secure the bolt, leaving the cable able to pivot. The principle is the same.
Also, please note that I did think of using a 3/8" shoulder bolt which would have done the job perfectly, but I would have had to have waited until i was back in the plant to use a drill press to enlarge the hole in the end of the shift lever to suit....and I'm not that patient. I wanted it fixed today!
But if you have the tools and materials available to you, a 3/8"-16 by 3/4" Cap headed shoulder bolt would fit perfectly with this. You could use a 1", and a couple of nylon washers as well.
This forum, and this thread have helped me out a lot, and hopefully this may help someone else, by increasing there options for this repair.