Not anywhere I’m aware of. Maybe the outer unit, then you need the inside, you need a licensed technician to install it, you need it to not look hideous and tank your house price. There is several thousand euros. You also need a larger unit because the rooms are too large to take one of the smaller units.

They're talking about window units, not heat pump systems or central air. It's a complete AC that sits in your window. It can't cool a very large space (even in apartments people may have more than one), but it's cheap and easy to install (and equally easy to remove). It might be unsightly on a house, but a lot of that is probably just cultural norms. They're very common in NYC, where a lot of housing was built before central air became the default.

I think you are thinking of mini splits, and not what americans would call a window unit. I got my window unit for $100 off craigslist and put it in myself without needing any tools.