since it's steel (and no, I didn't know that without asking) any good frame repairman could tig-weld (or braze) a new hanger onto the old dropout, assuming there is enough surface area left on the old dropout once the hanger is ground off. The replacement might have to be cannibalized from a donor frame with a good hanger. I can't tell you what that would cost, the repairman should provide an estimate if it's something they've done before. Might be cheaper (or same cost) to replace the whole DO, and if so they *should* find just a RH that will match the slot on the left...that option will ruin more paint (or chrome) than splicing the hanger alone.
Cheapest option of them all: lose the hanger altogether and use a "claw" adapter for the RD.