These are so common in the US – you can get them just about everywhere. But elsewhere they are impossible to find. Most of my refillable hand bound books use them and Europe does not use this paper size, so whenever someone goes to the US I ask them to buy some for me.
My favorite are the Mead ones which are made in Egypt as they have the best paper quality. This paper is not archival though so does not last forever but for notes it is just the business!
Interestingly, I always say ‘Mead’ even though the ones I use the most are Staples’ generic ones. I guess this is an example of a brand name which has become a generic
Below are some of my books which use the Mead Composition Book refills.
And my favorite country of manufacture for the paper: