I have never seen plain dry ice for sale anywhere, though I have not gone looking too hard. I have seen the dumping some liquid CO2 into a special sock method though.
It's dangerous enough (suffocation, freezing) that there are plenty of reasons to require an age minimum. I don't think I've seen dry-ice in supermarkets since COVID started, but I haven't been looking much either.
Never disappeared around here. A lot of people rely on it to get their frozen stuff home without thawing out. So it's more available in rural places where people will have a long drive home.
Ahhh, that makes a ton more sense now. As one of the aforementioned soda-bottle-bomb-making-youngsters, I had no idea what people's legitimate uses for it were outside of party tricks.
I think all my local grocery stores sell it and so do at least some of the ice cream shops. None of them really advertise this; you just have to ask for it at the cashier.
On Halloween, my grandma (I’m in the US) would dress like a witch and use dry ice carbonate homemade root beer she’d dole out to kids from a giant bubbling black cauldron. I thought grandma was an actual witch for a while there.
This kind of depends on the location/jurisdiction. The more rural you go, the more likely you can buy it. In a lot of big metro areas you'd be better advised to call ahead until you find a store that carries it.
I've seen several places requiring ID to purchase dry-ice to avoid youngsters making soda-bottle bombs with it.