Do NOT buy the U-line containers. They are polystyrene (PS) and the ink chemicals break down the container and it will relatively quickly disintegrate. You'll then have a mess and must throw a bunch of ink away.
Ideally you want HDPE plastics which is what most all factory inks come in (look at the stamp on the bottom of the container). This plastic is flexible and less prone to explode when dropped and is chemimcal resistant
PP (polypropylene) is also chemical resistant, but more stiff and brittle.
I have search endlessly for quart containers and finally somehow talked this vendor selling to me direct in case quantities. thecarycompany.com. Only had PP in the 32oz wide jar. Likely, the best bet is to just call your ink distributor that mixes custom inks, pay the premium price, and ask them to sell you some of their quarts.