Quarter Letter Sized Binder

I'm trying to find a binder which would fit paper which is a quarter the size of US Letter paper (i.e. 4.25"x5.5"). I have found a few binders and solutions for A6 paper, but I believe these are different enough from quarter US Letter paper for it to not work properly (A6: 4.13"x5.83", so about an eighth inch narrower and a quarter inch taller).

This brings me then to three possible approaches:

1. are there any binders sized for quarter US Letter which are simply available for purchase, and which I've just failed to be able to find in a product search? Apparently C-line used to sell one in at least Canada via Staples (as per: this reddit post a few years ago), but looking through C-lines current products is not showing something as the quarter US Letter size.
2. does anyone use an A6 binder which they've found is fine for holding quarter US Letter paper?
3. if all else fails, am I stuck with a DIY approach like this post showed for A6 binders about a year ago?