Just did some research, you want this kind with the lock on 4 sides and a rubberized gasket: "Glasslock".

Square should be better than round.

These are 2 compartment, which sounds even better. This is the style you want:

https://www.amazon.ca/dp/B07CZPZ87F/

We just got a set of the single-compartment version and they are absolutely fantastic. The flat top allows a small post-it note for the date the food was made and lets them be stacked in the fridge.

We got ours at Sam's Club.

Does Sams club have large sets of 1-person lunch sizes? Or can you only get the 38 packs or whatever of different sizes?

I dunno for sure as it was the work of my wife and daughter, but it was a fairly big box of `em. We rarely go out to eat so lots of food goes into them, from olives to butter to thawing blueberries to hummus to leftovers. It looks like they got the 24-piece Glasslock set for $25.

American Pyrex isn't, it's a Chinese knock-off that was deified as the brand. But it's not the original Pyrex and it doesn't stand up to heat.

I know, but it beats plastic. I’m not smashing it with a hammer.

American "Pyrex" is actually less vulnerable to hammers than borosilicate. What it lacks is resistance to extreme temperature changes.