You can buy them from a lot of people. They in turn buy them from one of two companies which will sell them to you as easily as to a middle man. That would of course be either Moog (a Federal-Mogul company) or Eaton. Brakes are made by two companies also; Bembro or PBR but neither will talk to you because you won't buy enough to justify the paperwork, and both are European and don't think much of Americans. (weall actually PBR is R-straliain but they speak English with an aaccent).
Brakes I always recommend that you buy a complete kit. Master cyclinder, and wheel cylinders matched to each other and all of the hardware that allows things to bolt on without adapters or spacers or surprises in handling.
Fot lowering a car I recommend a lowering steering Knuckle (spindle raised) to lower the front and lowering springs with air bags in the back.