There are numerous places you can purchase refrigerant either through online websites, in a retail setting, or purchased directly from a refrigerant distributor. Where to buy is going to be determined off of what kind of refrigerant you are looking for and what kind of quantity you are looking at.
If you’re looking at just one or two cylinders of refrigerant than the easiest place to purchase would be online either through Amazon or through E-Bay. These two sites allow you to purchase any type of refrigerant by individual cylinders as well as providing ease of use.
The only catch is that you will need to provide EPA certification. If you cannot provide certification than you will not be able to purchase.
If you are looking to purchase larger quantities of refrigerants such as five, ten, twenty, or even a pallet of forty cylinders then I would recommend contacting refrigerant distributors. I have compiled a listing of various refrigerant distributors throughout the United States. You can view the list by clicking here.
When contacting them know that the more you buy the cheaper your cost will be and it is best to shop around between at least a few distributors to ensure you get the best cost.
Lastly, if you are looking to buy pallets at a time I would consider going direct with the manufacturer of the product. DuPont, Honeywell, Chemours, MexiChem are all manufacturers here in the United States that could be partnered with.