I haven't been on this site in months, so please forgive if this has already been posted. I did a quick search and didn't see anything..
I found the niftiest thing today, for "our types". It's called a Pen Loop - google Leuchtturm1917 pen loop - they sell them on amazon. I'm including a link, if that makes it through on the posting. Anyway, you can add a pen loop to anything. I stuck one on my circa compact agenda today and now it's perfect!