I haven't priced either chemical recently, but it is a simple matter to make PO from oxalic acid, potassium hydroxide, and H2O. Both of the components can be had fairly cheaply on their own.
For example, check out:
for prices of the composite chemicals.
I mix my own in several gallon batches every so often. It is much cheaper through that route. Last time I ordered, I got about 25# of each chemical. I also use the oxalic for other things, so it was not really an issue to have it on hand.