You could take a look at Levenger’s Circa line of products. Their stuff is reasonably fountain pen friendly (and if you end up liking it you can cut paper of your choice to fit). I prefer bound notebooks, but still have some Circa stuff because it’s just a great system.
You didn’t mention how you would carry the notebook so if you are hoping for pocket, it might not be the best. It’s not perforated but you can easily pull the pages out for scanning.