If you look closely at the spool/valve, the broken part/tang looks to be a separate piece, mayhaps screwed into the spool. You might could check with hydraulics shops to see if they have one. If you can unscrew the broken piece, any good machine shop should be able to make a new tang.
At any rate it's a good bet the spool/ valve will have to come out for the repair or replacement.
Have you checked Toro's site? They might sell just the spool.