This is a refillers forum, so members usually don't buy ready to use cartridges.
I buy non Oem cartridges every once and a while, but most of those products are of poor quality. Cartridges for Canon appear to have a bad flow. Cartridges for Epson often give clogging.
The only brand that is satisfying is Peach, which is sold by Lidl under the name United Office. It didn't show these problems and the color and density are the same as with OEM ink.
Another way to get ink is to have your cartridges refilled in an inkstation. They often use quality ink.
@Adrian_Watson Do you want compatible materials for an ink jet printer or a laser printer? And for which make and model? Knowing your location might also help locating a supplier.