Leuchtturm1917 is the brand that has the most different sizes and colors of notebooks. The range is incredibly wide and here you should be able to find a notebook based on your taste and color, format and hard or soft cover.
Notebooks have extra everything with index, pocket at the back, elastic band, page numbering. In that series of notebooks, however, the paper is 80 GSM. If you want thicker paper and notebooks from Lt, the books with 120 GSM and Bullet Journal edition 2 apply. However, these are only available in A5 format, with hard covers and a smaller range of colors. So that you keep an eye on this so no surprises happen.