Custom make your knurled/sloted knobs with captured nut. Some assembly required.
I was using them to keep my Replicator's Build plate tightly level until I have changed the entire Z stage (testing it now, coming soon...)
The properties of the knurl cannot be modified :( well, you can change them if you download the OpenSCAd and change the values to taste.
The washer acts as a nut retainer, thus, it needs to be glued, melted or press fit. I choose to melt it with an acetone vapor bath.
You could also play with the nut's across flats distance to get that nut so tight that no washer is required...