Step 8: Add a comfy "knob" with whatever you like
Keep in mind that the larger the diameter of your knob, the more precise your movement of the indicator can be. If you really want to be able to move the indicator just a hair's breadth, a bigger diameter knob is the answer (but it will also take longer to move wide distances).
I found the original knobs to be pretty comfy. They were both screwed and glued onto the metal dowel, so I clamped them down hard in a vise and unscrewed the knob with pliers.
Note: if you choose to use pennies or other currency, please be aware that it will increase the cost of this project. Of course, you can get a refund any time you like...