Google will be your source. Many local distributors will NOT simply because HVAC is not really DIY. For a gas furnace, a permit is mandatory, and a homeowner can do that in some states, but we are messing with gas here.
For the air conditioning side, a DIY does not have the EPA certificate to purchase and work with R22, and does not have the THOUSANDS of dollars worth of tools....recovery system, vacummp pump, gauge manifold, brazing set, etc. Not to mention the knowledge of how to set your superheat/subcool, etc.