I am sorry the fix which worked for me didn't work for you. I haven't been back to this site for a couple of months since I have been busy getting
a real estate license.
If you can get a couple of broken handles from a salvage yard, maybe you can try again. The one I repaired have been in seervice for a three months and are doing fine.
You can always extend the rope out the window and attach a couple of lemons to it. Then park the car in front of the dealership where you bought it. That might tempt the Chevy people to stock that little plastic part as a separate item.