Small update;
after all the paperwork I got my Glock and bought an adapter plate for a whopping 100€ and second-hand ROMEO1 for 250€.
In my calculation, €350 for the set was reasonable, as the red dot is sold here new for €470.
Unfortunately, the reflex sight arrived defective, which I only noticed later as I was still waiting for the paperwork and the gun at the time.
However, SIG offers a 5-year warranty and I sent the reflex sight to our importer some weeks ago with the note that I would like to make the Sig Sauer Electronic & Tritium Component Limited 5-Year Warranty used - which, to my surprise, worked without any problems, I didn't even have an invoice or receipt.
As the ROMEO1 is unfortunately not in stock, it first has to be imported from the USA, which is supposed to happen this week.
Long story short,
From the idea in February, if the ROMEO1 arrives in a week or two, it has now taken me over 3 months to get everything together the way I wanted.
In any case, I won't be buying any more second-hand optical sights, that cost me too many nerves, but on the other hand, if everything goes smoothly now, I've got a new ROMEO1 for a very good price.
I'm looking forward to it.