Here is plan B

Buy Phosphorus and Potassium separately.
Phosphorus is 0-45-0 and $17.45/bag
Pot Ash (Pottasium) is close to 0-0-61 and $18.95/bag

So one bag of 0-20-20 has 10lbs of P & K

50lb bags of the above has 22.5lbs and 30.5lbs respectively. So for the same amount of money you can get double the product.