The plastic knob on our Gas cooker was loose as a small piece broke off.
This is a replacement knob. It suits a Miele Cooker
To assist in deciding the correct knob to download, the essential dimensions are:
To suit 6mm diameter shaft (5 mm Across the flat).
I had to print 3 development prototypes to determine one where supports would not be an issue.
The successful print used 0.2mm layer height and was printed laying on its side with the grip vertical.
I printed another with the center shaft on the bed. It results in good finish.

I used Fusion360 to create the Stl file.