Here is why the some of that stuff is still out there. The bike guys quit doing abything but 836 kits for several decades. The only ones that did any sohc stuff, and single handly keep the limited aftermarket demand going, were the three quarter midget racers.
That motor ruled in TQs for a long time, until Don Vesco figured out the GSXR750 suzuki.
Since then, there has been a small vintage demand, but nothing like it was. The people who make the cam billets, Engine Power, would have to cast several hundred cores, finish them all but the lobes, then put them on the shelf and wait for the cam grinders to call. I guess it took so long to turn over the last batch that they won't do it anymore. Inventory needs to turn several times a year.
As for rods. The breakage was always in the beam. Bolts were not the weak link, altho I remember putting some car bolts, maybe 289 Ford in some Honda rods. That is why no one ever made a mid grade rod. There were only 836 street guys who were not hurting them much, and the alky TQ guys who needed Carrillos.
One could probably get good rods made in China for about $12.00 each, but wopuld have to charge 10 times that much for them because thay would have to sit on them for ever.
I might know where there are some 970/1000 pistons. I will check.
Jay