I don’t have a Kirsten but I do own a Falcon and a Viking (copy by Dr Grabow).
I need a Kirsten.
Any pointers on which era or style?
They all have O-rings after Gen 1. Gen 1 was fabricated to be perfectly sealed without o-rings. If it’s your first and you are unfamiliar, I would buy one from dkmetalpipes.com (kroozrs on ebay) he specializes in Kirstens/metal pipes, he made an adapter that you can make a kirsten both bent and straight. (Get Bent adapter)
Theres so much, bowls made gen 1 are not interchangable with the future gens, but He also made an adapter that fits Gen 1 bowls to all other Gens.
Dkmetalworks Restores them and all that. You can message him on ebay. He is very knowledgable on the brand. They still make brand new Kirstens for purchase on their website as well. The o-rings are plentiful so I wouldnt worry if you even have one fail.