[sdiy] I need your knob expertise

[MTG]

I'm looking for a relatively low profile knob for a rotary switch. 1/8" 
diameter shaft. The switch does seems to require some force to turn, so 
knob diameter should not be tiny. I don't know for sure yet, but 
probably >= 1/2" in diameter and about the same in height? It's for a 
retrofit mod that will appear on the outside of some NOT rare vintage gear.

Curiously I have zero knob stock,  =:-o  so rather than just buy a pile 
of stuff to test off eBay, I thought I should ask here first.

I'm using a Grayhill 4 position rotary switch ($$$) because it seems to 
be the only thing I can find that will fit in small places. Anyway it 
has a 1/8" shaft with "a bit" of a flat spot.

http://www.mouser.com/ds/2/626/Rotary_56-335299.pdf

GB