I just had a similar problem with bent pushrods. I talked to a guy at McConnell Machinery located in Lawrence, KS. I can't remember his name though, sorry! He can get them new ($52 EACH) or he said that he may have a used set for $15 each.
I didn't want to spend the time waiting on the used rods and wouldn't pay that much for new so I straightened mine back out. With a ball-peen hammer and some patience they are now mostly straight. My engineer father-in-law said that if I could get them back to within 1/32 of an inch that they should do fine. I mowed all afternoon yesterday through some pretty heavy stuff and the tractor ran fine. I haven't pulled the valve cover again to see what happened to the rods or re-check valve clearance but there was no noticable change in the motor sound or power.
As for the rocker arms... I don't have any leads, other than McConnell.