I recently moved into a new home (built in 1960) and need to replace a
broken sprinkler-head of my in-ground irrigation system. The problem
is that the supply lines in that sprinkler zone are entirely iron, and
the riser to the broken sprinkler-head was completely rusted-out. I
couldn't remove the rusted iron riser from the supply line (it's
rusted in place), so now I've got a hole in that sprinkler zone.

I know the long term solution is to dig-out the supply line and relay
PVC, but that's not an option for me right now. Is there anything I
can do to attach a standard 3/4" PVC riser to the iron supply line, so
I can get the sprinkler system functioning again?