As indicated on the EPA Web Site under "Refrigerant Sales Restrictions", and as of January 01, 2018, refrigerant R134a and R1234yf that is sold in containers of 2 Lbs. (32 oz.) or less, does NOT require EPA Certification to purchase.
This is directly from the EPA Web Site......
" Small cans of non-exempt MVAC (Motor Vehicle Air Conditioning) Refrigerant for example, (containers designed to hold two pounds or less) that have unique fittings, and self-sealing valves, can continue to be sold to persons without EPA Certification for DIY (Do-It-Yourselfers) on their vehicles.
This item ships UPS-Ground as a Hazardous Material Package under the "ORM-D" Limited Quantities exemption as listed in DOT-US CFR49 shipping regulations.