I bought this and it works pretty well. It's about 2.5" tall, advertised as water-tight, though I haven't put it to the test. Can't speak to the capacity, because I haven't measured it specifically, but I'd say it can hold more than 20oz. If you browse Amazon a bit, there are single and 3 compartment versions as well.
I got mine on sale on Amazon. 40 containers for 31.98. They are usually $50 for 20 but they are on sale right now for 15.99. I got 2 orders. https://www.amazon.com/dp/B0742KGQG8/ref=cm_sw_r_cp_apa_5FuHBb0DQRCT7
Want some plastic ones? They look like this and I will mail you 10 or so of them if you DM me an address.