Start by going to the big box stores and see if there are any in the pattern and color/blend that they sell. If there are any in their inventory find out who they are made by (brochures, pallet identification, etc.) to see if they are made by a major manufacturer.
Check the manufacturers out to see what they can actually supply, which is far greater than what a "big box" inventories. Most manufacturers will not sell to individuals because of the cost, but do provide a list of dealers. A manufacturer will usually no price products below the price of a major customer for many good reasons.
If you need a reasonable amount of any pavers, a dealer may be able to deliver them for a total product and delivery price cheaper than if you try to drive, handle and pick up a few tons of pavers.
Clay brick pavers are limited in use and selection, but interlocking concrete pavers are much more commonly used and have a much wider range of shapes, thicknesses, colors and blends. If you are looking for the larger (over 10" and thinner) units you are looking at stepping stones that are totally different.