I have 2 (somewhere, I can't find either, grandsons probably "borrowed" them).
1. Leather pouch, a 50 round box of .22LR will just fit. I have removed the box and set the plastic tray inside, filled with ammo. Loose dumped is faster and my preferred method.
IIRC, I got it at Academy.
2. Mil-surp, with Alice clips, a little bigger than 50 round box, will hold 100 loose rounds. I had 3 off these, but gave 2 oldest grandsons 1.