I would argue that any old 256/512MB first gen Pi would suffice, and those are easily found second hand. Not everything involving a Pi requires an 8GB Pi 4 model. Most things involving a Pi don't even require a Pi.

Some stores in Finland have them. But you might be correct: Looks like the stores in Finland have stock left but seem to have difficulties ordering more. The demand must be so low, that they're still only slowly running out of the stock they have.

You can buy a starter kit, plenty of them. It's double the price but if you starting with rpi it's necessary.

Don't you always have one stored for "that one project" which may come one day?

I do...