Product review (4 stars): Universal Cookware Pot Plastic Grip Glass Lid Cover Knob
I have a Crock Pot that the glass lid plastic grip broke on.  Of course, they do not sell replacement parts for that!  So, I had to look for a different way to fix it or go out and buy a new crock pot.

While looking on Amazon, I came across this item and decided to give it a try.  While it does not have the ergonomic design of the original, it certainly is functional and lets me continue to use my slow cooker!  There is enough room for your fingers to fit around this without touching the hot glass.

While not a perfect solution, it certainly does work and I have been using it now for almost a year without issues.