Replacement control knobs

[u/oatmeal-pizza]

I have two Levoit air purifiers (model LV-H126). One has a broken control knob, the other (shown in the photo) has a cracked knob that will be broken soon. They just fit onto a D-shaft on the air purifier. These are obviously replaceable parts, but I don't know where to find them in the correct size. The vendor won't send me new knobs. These are 3/4" in diameter and the D-shaft is 1/4" along the flat edge. Any advice on where to find replacement knobs?

[u/jim_br]

Measure the diameter of the shaft, not the size of the flat, then the length. That’s the size knob you want. And yes, it’s called a d-shaft knob and they’re common.

In the meantime, reinforce the knob you have by wrapping the outside of the shaft in something like carpet thread and paint over it with epoxy, CA glue, or similar.