Hi Arsenio!

> I asked the food market store manager and he stared at me blankly.

Ask for pickled tsa tsai. Or stem-mustard. Or salted cabbage turnip ...

> I guess "kohlrabi" isn't a recognizable word to him.

Well - I was stunned to find this german expression here ...

> What am I looking for? How do I recognize it? Are there any
> substitutes that I might actually find on the shelves of my
> local Asian food market?
>
> Any leads are much appreciated.

Google is your friend - that way I found "tsa tsai".

Bye, Sanne.