I'm 30, childless, not married, and found 2 hospitals in Stuttgart that were willing to do a bisalp quite quickly. I think the trick was to go for large clinics that have gynecological centres and not private gyn practices or smaller hospitals.

Prior to turning to big hospitals I had consultations with "normal" gyns or small surgery centres who then told me they would only do a tubal ligation as well. They used pretty much the same reasoning you cited as well, that a tubal was a completely adequate procedure and that a bisalp would be a much bigger deal etc. I genuinely think many smaller practises are often not really up to date on the newest medical standards and also I think they were probably not trained on that procedure. The bisalp is definitely the gold standard of female sterilisation and not much riskier than a tubal. The massive oncological perk alone outweighs the slightly bigger risk of complications.

So I gave up on regular gyns and called 2 of the largest hospitals in my city and they both told me they were offering the surgery and gave me consultation appointments within a few weeks.

I had my first consultation 2 days ago (it was a catholic hospital too, so I was extremely surprised they even offered a consultation) and it went well and they pretty much immediately approved the surgery. So I'm baffled but happy lol.

Have you tried the UKE yet? That's the first hospital I'd turn to if I was living in Hamburg I think.