R-452A was just recently approved by the Environmental Protection Agency’s SNAP program so it is has not yet seen mainstream usage in the United States. That being said it is very difficult to just buy one jug of R-452A at this time. I have contacted a few of my distributors and they have said that they cannot sell just a cylinder of R-452A. If you are looking to purchase 452A in multiple jug quantities then they would be able to get you an order placed.
R-452A is replacing R-404A, but R-404A is still seeing widespread use across the United States. So, 452A’s demand at this time is extremely low. Most refrigerant manufacturers such as DuPont or HoneyWell only sell refrigerants in pack quantities such as 5, 10, or 40 pieces. A distributor is not going to buy a pack of R452A just for a sale of one cylinder. They’ll be left with the excess cylinders in their inventory and since the demand is so low right now it will never sell.
If you are really looking for just one cylinder of 452A I would suggest contacting either your local ThermoKing or Carrier distributor and see if they can sell you a cylinder. As time progresses 452A will be easier to purchase, but as of right now (June, 2015) it is still a rare find.