There are several monsters that will drop these armors. Georappella or whatever will drop a weapon with No Encounters sometimes. You can also use Purifying Salts which you can bribe out of the Ghost-like creatures or get a whole bunch from the Monster Arena. I think to get them from the Monster Arena, you have to catch one of every monster in the Cavern of Stolen Fayth. However, I am totally unsure of the requirements to obtain the Purifying Salts from the Calm Lands Arena master.