Thanks all. That's just it, A4 and large wallet size are not a problem to find, but A5 notebook doesn't seem to be a thing in the UK, whilst it's available in the US.
@WakingUpDistress, those bring back memories from when I was growing up as I used those for school, but they're just to place pencils and felt tips in the elasticated loops. I have a similar one for my crochet hooks and I love it!