Update: I found it.. It's not that great..
It was cheap enough that it was worth to try but I would not recommend filofax. The holes are all wrong for a regular spiral bound..
Pictured is the filofax ruler insert thingie. As it was, then cut to fit in my notepad, then in my notepad.. (the rhodia dotpad A5 for those who want to know)
In a decentralised social media it makes sense to host yourself. That's what we decided to do. This instance is run by two nerds, mostly for the why not of it. Feel free to join, and we'll hit you up with an "Hi, who are you?".