As of today, in June of 2015, yes you can. However, the market on CFC/HCFC refrigerants is highly regulated. You will need to be 608 certified with the Environmental Protection Agency in order to purchase or handle any CFC/HCFC refrigerant. You can read more about certification by clicking here.
CFC/HCFCs are highly regulated due to the Chlorine that they contain. In the wrong hands a technician can vent the refrigerant into the atmosphere which would cause direct harm to the O-Zone layer. The regulation is in place to ensure that anyone who buys CFC/HCFC refrigerants knows the proper way to handle.
The most common CFC/HCFC refrigerants that people will be looking to purchase are R-12 and R-22. It’s rare to find an R-12 system now a days but R-22 is still fairly common across the United States. Both R-12 and R-22 can be found by shopping on E-Bay by clicking here. (Be aware if you purchase on E-Bay you will need to provide your certification number.)
****UPDATE AS OF 2018***
The EPA’s refrigerant restriction laws changed on January 1st, 2018. As today as I write this you will now NEED either 608 or 609 certification in order to purchase HFC refrigerants. The type of certification needed depends on what kind of refrigerant you will be purchasing. As an example, you will need 609 certification to purchase R-134a.