In Oct 2022 I booked Finnair AMS-HEL-BUD for 2 persons for next April. Today Finnair did email me that the AMS-HEL flight is cancelled and that they don't have alternatives and that I can opt for a refund.

I called and chatted with Finnair to ask them to reroute me AMS-LHR-BUD (BA) on the same day. They refused and offered me DUS-HEL-BUD or BRU-HEL-BUD (both AY) instead. I won't wanna travel to these airports (extra costs and travel time) and pointed out that EC261 specifies that they have to provide alternative flights under comparable conditions and I did give them the BA alternative again and if not possible a KL and a LH one. They refuse and say their backoffice has not authorized them to rebook on other carriers and rebooking on other carriers is against internal regulations. When I pushed a bit more (but kept being courteous) they closed the chat.

When I read article 8 of EC261 I see "re-routing, under comparable transport conditions, to their final destination at the earliest opportunity;" so for me that means they have to rebook me on any carrier on the same day and class. Am I right? If so, is there any way to reach someone at Finnair that has the right authorizations to do this?

The BA flights are much more expensive (for a regular customer like me) so that's why I don't want a refund. I booked Finnair because I'm OWE so I have lounge access and free emergency exit seating and I'm 201cm long. The KL flight is only a bit more expensive than what I paid originally but then when including seats at the emergency exit we are talking about maybe € 50 per person more.

If I cannot reach anyone at Finnair with the right authorization what would be the next best option?
1: Buy BA tickets (+/- €750 instead of the €350 I paid at Finnair) and send Finnair the bill
2: Buy KL tickets with emergency exit seats (+/- € 450 instead of the € 350 I paid at Finnair) and send Finnair the bill
3: Buy KL tickets without emergency exit seats (+/- € 400 instead of the € 350 I paid at Finnair) and send Finnair the bill

I understand I might have to pursue this issue in (small claims) court, but which option would be the most comparable? Or should I take the refund and cut my losses?

And yes I know € 100 isn't a very big amount but it's also about using my legal rights.