There are a few knob designs out there for the (tr)uSDX but I could not find one small enough for what I wanted to do so I made this one. It does require some modification to the rotary encoder component. 

It has a thin arm that you can use to spin the dial, but also a knurled knob for press and turning for volume and menu select.

Here is a quick video showing "spinning the dial"

I spent a considerable amount of time with a Dremel trying to get this to press fit on just right. In hindsight, you can probably just heat up the inside of the knob with a soldering iron and then pressing it onto a shorted encoder shaft.