Though it's not anticorruption but for souvenir purposes. I have quite a few of them from various tourist attractions.

So have I! I’m puzzled but delighted by how widespread they are-and in fact I’m personally aware of vending locations in several places not reflected on the official map [0].

[0] http://www.euro-souvenirscheine.de/map.php

There's also the Greater Japan Zero Yen Note https://www.moma.org/collection/works/136620

(The background to these is a complex of art projects and a court case, but it came to mind)

Now we only need an infinite euro note.

It will be fun paying with it and getting change back.

You’d just get the same note back.

We need at least two, for countable and uncountable infinities.