a traveler's notebook isn't really a notebook. It's a notebook cover that holds several smaller notebooks.
When the notebooks are full, one can simply take them out and put new ones in.
Now, I go through a lot of notebooks. There's always one or two in my bag. I have a book for my
bullet journal, one for my weaving patterns, one for my garden, one for my writing drafts, one for my knitting, a spare one, one for my bag... There's a lot. I love the A5 size and my absolute favourite so far are these thin volumes with a kraft paper cover. The problem with the thin journals is that they don't hold up to daily wear and tear. Thicker books are nice, but having half a dozen notebooks in my bag at one time is crazy heavy. I also hate to start a big notebook only to discover that the paper quality isn't sufficient for a fountain pen.
We can buy notebooks inserts and covers. Amazon has some lovely A5 size inserts with nice quality paper.
Or we can make our own. That way we have full control over the size and quality.
and a more complicated way of making a notebook