ISO paper sizes are used pretty much everywhere except the US, it's not exclusively a European thing. It's like the metric system, if someone's using sensible standardised units they can be from anywhere and if they're using weirdly arbitrary units they're probably US.
Assuming you talk about a paper-ringbook-type of thing to write on with a pen, you could buy the ones where the last page is made of cardboard to prevent bending.
These sizes also come as books, hardcover thing with blank pages inside, hard to bend.
If we talk about an electronic device, just please dont sit on it ;)
I eventually just gave up and started buying expensive notebooks. The cheap ones always fell apart before I finished them, so at least this way I get to the end!