Disc blades are "generic" for the most part. You'll need to know diameter, size and shape of the axle. (ie 1"... round/square)
Agri-Supply can ship them to your door for a fair price. Some TSC stores carry them. Any GOOD farm equipment dealer will be able to get them for you. I bought a set for a Massey Ferguson disc last fall. Got 'em through Agri-Supply. UPS-ed to my door for less than I could buy locally.