If you are not satisfied with the sizes of the adjustment knobs you find in Thingiverse, here you can customize one to your liking....

You can choose diameter of the knob, if you like spikes, how many and what size...just as you draw it...

It will leave a void for the nut so you should insert before the printer add the top layer of the nut "cave", or if your printer can bridge it just do it after printing. The radiuses of the for the nut's cave are listed here, then consider your printer's accuracy and add 0,2mm or more for the nut to insert without problems (I usually add 0,2mm and fits perfectly). Consider leaving the center hole 0.5mm bigger than the screw size.

M5 9mm M4 8mm M3 6mm M2.5 5mm

I created these links where you can find all common filaments and spare parts at the best prices. These are just links to selected eBay and Aliexpress items, where I normally buy spare parts and materials for my printer, prices are excellent and products are good. If you buy something from here you will support me a little bit to make these projects.

1Kg PLA Filament - eBay