OP, PPs are trying to help you, but you are being very frustrating.
Many PPs have asked you whether you have any contact with any adults at all, but you refuse to answer them. It is hard for people to understand why, if you have children at school, you are unable to ask any of the other class parents. Even if you don’t “know” them as friends, as long as they have seen you rocking up to the school for a couple of years, that’s all that is needed, and I am sure that there will be a parent who has a passport and can sign for you.
So, is it that you really never have any contact with any other adults ever, or is it that you don’t want to ask? If you could explain why you think there is absolutely no one who can sign for you, then you might get more sympathetic responses.
But as many PPs have said, yes, you need someone to sign. The rules are there for a reason and there is no way around them. So you need to either pluck up the courage to ask a parent of a classmate, or you need to forget going abroad on holiday.