Binder clips are probably my favourite “hack” to get page markers in notebooks that don’t come with them. They are dirt cheap and works great. I use them both with my Travelers notebook and my pocket sized notebooks to be able to find the first empty page as fast as possible.
I don’t use any fancy ones, just the plain black no-name ones you can find in any office supply shop. And I’ve had the same box for years.
They are durable, and stay put. My only complaint about them is that I wish I could find a version that was smaller and didn’t get stuck as easy when I take notebooks in and out of my bag.