That looks like it might possibly work. The waist packs I've tried tend to be too small for phone + wallet + keyring + glasses. Unless they are huge lumbar packs for hikers, and those tend to mess with my gait (or balance or something.)

The main thing I carry for teaching is a 5x8" pad of graph paper with 3 felt tip pens. (There are some advantages to carrying it in a little vinyl folder with a side pocket. But that adds more than a quarter inch and isn't always worth it.) A couple of the blazers I wear to teach in winter are not really flattering, but I wear them because they are the right level of businesslike and they have 5.25"x8" pockets.