Reddit mentions of S chestnut L-50 50 pieces Nippon clinofibrate graphics slide clip size L (japan import)

Why not try a 20 hole or 6 hole binder system? 3 rings are awful.

I'd also recommend a sliding binder, which I can't seem to find any mention of in English. They're like six ring/20 ring binders but have a flat spine that serves as the closing mechanism, and could be good for labeling if you wind up putting it on a shelf or in storage. I have one in a Bible/A6 size (really tall and narrow), and it's actually kind of handy and neat.

Here's a site that sells them in English, but the store doesn't label them any differently (loose leaf binder) than other binding formats. One downside: I've never seen them bigger than A5, so that may not work for you for scanning in bulk.

If you're stuck on lettersized/A4 paper without holes, binding bars might be your best option. Those seem to come in a max width of 1/4 inch, though, holding approx 40 sheets. (This one claims to hold up to 100 sheets, but who knows?) If that's too few...maybe some report covers and binder clips up the side either traditional or newfangled?

I knew a girl who used rings and two holes in her paper (though you could go for just one in the corner to reduce hole punching time) for everyday carries and then put her paper in more formal binders/bindings when she was done. You could just label giant binder clips and report covers for storing the stacks of paper, plus a bookend to hold it all in place until the shelf is full.