Several places have it available online. You will want to shop around for best prices. Shipping can vary from one place to another, some like Grafs include it, but if ordering over 3 jugs, it may be cheaper to go with another supplier that has a lower price per jug. You will have to pay HAZ MAT fee of $22.50, and usually about $10 for Shipping. Most places will ship up to 48 pounds for the same shipping and Haz Mat charge.
Midsouth, MidwayUSA, Graf & Sons, Powder Valley are some places that sell it. Powder Valley has it for $26.65 per jug, Graf has it for about $30 per jug which includes shipping. You would still have to add in the Haz Mat for both.
If you go to Powder Valley's Home page, click on "Powders", then click on "Accurate Arms", Blackhorn 209 will be on the top line.
The retailers are charging just about anything they want for it, I have seen it for $29.99, $34.99, $39.99, $43.99, and sit down $48.00 just last week in a shop. I know these guys need to make a profit, but that last one is getting his whole Haz Mat fee back on the one jug.
It is an excellent powder, and I use it exclusively in my 209 primer rifles.
Tip: If you can get a few guys together and pool your money, you can spread out that Haz Mat and shipping charge. Another option is to see if your local range will add it to their order.