They sell these for $1 each. They also come in different sizes.
Sheesh, I can't believe it's $16 for a pack of 5 now. When I bought two years ago on Amazon (I don't live near a muji.), it was $10.
Their pens/stationary work so well, and everything is pretty affordable.
I understand the appeal of having a nice, left handed notebook, but they've existed in Asia for years as standard-issue.
I found a handful of MUJI A5 notebooks on Amazon that are bound like composition notebooks with thick paper covers.
These are both advertised as A5 notebooks. First link with dark covers features notebooks with a square grid layout and the second features ruled paper. Both of them are multi-packs of notebooks, but they feature notebooks with 30 sheets, so you can decide if that fits your needs.
If you want more pages, there's this 72 page version of the standard ruled paper.
Once again this one has a thick paper cover and is bound like a composition book. If you're interested in looking for more, just search "muji a5" on Amazon and see what sticks out for you. Also, the paper is quite good. I got some A6 sized ones and they hold fountain pen ink quite well.
hopping in to say - I think the notebook in the picture is indeed from Muji, because it's one of my personal favorites! it's surprisingly good with fountain pen ink.
if you're interested you can sometimes find them via the Muji website, but their stock isn't super reliable (at least in the US). I usually buy them from etsy/Amazon - here's a link:
Are you referring this This example?
I don't use the highlighter color ones, but they seem to be cheaper right now than buying separately?
For calligraphy: Tombo Dual Brush