I was not familiar with Kölsch (although it mainly is just top fermented from my understanding*) before Köln, but now that I had several while in Germany I have found a few here!
Berkeley Bowl has one from Ballast Point.
As well as one from Cali Craft , the Cali Cöast.
They tend to be less bubbly due to the way they are fermented which means you can drink them a bit more than a beer with more bubbles.