hi
you can purchase brand new paint cans at housepaint stores, that sell to professional housepainters [ ie not walmart / home depot type of stores]
here in Canada they cost about 3$ for 4 liter can [ maybe 1 gallon american ]. I buy them often to store material like nails, or mix paints etc. Sturdy and stackable.
I'm sure if purchased in bulk, they'd be cheaper.
Someone mentioned plastic paint containers. EEEEk..industrial non-food grade plastics-- I'd bet those slowly leech nasty fumes
and worse it will damage art
