They are difficult to find and not cheap. Sometimes in the $150 range! I looked and Rock Auto has them listed for $75 each plus shipping. But given the rarity I'd be a little suspect. In process update: I tried to put the rotors in the cart and they said they were not available.
I did notice that just about everywhere stated something like "sedan/wagon... not wagon." I don't think the wagon had any different rotors than a sedan. I'm guessing that it means the wagon maybe only came with discs on the front (because of the potential weight???) where as the sedans, some models had drum front brakes?
Are yours bad? Can they be turned? Can they be used "As/Is?" Do at your own risk and liability but they may be OK even if they don't look pretty. There are just some parts you grab when they are available. I say this for the future because the minute I heard they were hard to get (about 2008) I bought two at Pick Your Part. They are decent and I paid $8 for both. And, sorry no, they are not for sale - at any price. Maybe there is a junkyard that has them. Just don't mention the rarity or you may pay for that slip of the tongue.
Sorry for the bad news. Hopefully it has a happy ending. Maybe someone here has them for sale at a decent price. And, just a FYI, the steering rack and the spindle (tie rod end) are specific to 1973 as well.
Question to others, is the 74 up crossmember adaptable (and, yes, I know it is welded in)? I just never let a little weld stop me.