…well, most of my notebooks!
My favourite places to buy notebooks from in Nigeria are Miniso, ASOS (they stock a nice variety and they deliver to Nigeria) and department stores like H-Medix. If you spot a notebook you like in Miniso, just grab it immediately as you might never find that particular one again in any of their stores.
The last time I was in the UK, I got lovely notebooks from Muji, Flying tiger, TKMaxx, WH Smith and Wilkos. Stores like Primark also stock notebooks.