Part - shower knob - kohler - coralais

[louky]

I'm simply looking for info on where to buy a replacement shower knob. I swear none of the ones from Lowes work with mine, not even the "universal" ones. Any info in where to buy is appreciated. Pics coming....

 

[louky]

Here's the part it needs to attach to and this piece slides onto a square rod. Nothing at lowes is square and when i look at parts online, most of the knobs don't show the inside portion to verify it's a square slot.