I think I know what you are talking about, I have trays like that and they came back in the days with that old freezer that still works good enough. that plastic is really more sturdy than anything today.
Unfortunately they started cracking so we were looking for new ones, but all of them are made of some kinf of cheap plastic or silicon, which I don't want to use, because just by looking at them I feel they probably "leak" lots of microplastic over time. also the cube holes are not trapezoid so its often hard to get out the cubes without damaging the tray, and adding even more microplastic to my drink