You might try Chevy2Only. They have a stockpile of not-currently-reproduced parts available for sale. Sometimes Modern Chevrolet has some of these old parts available too. Ebay is a good source for this most of the time also as long as you trust the seller.
I think that the idler arm frame bracket and center link are the only two steering linkage parts that aren't being reproduced for the front suspension for the early Novas. All of the "wear parts" are readily available from most of the resto parts houses.