you aren't sunk as far as headsets, but choices with <31mm stack height are few: the Dura-Ace HP7600 is one (but modern) and the Tange MA-60 is a better "classic" looking choice but just a hair over 31mm. I bet you can get it working with thinner or no washer, plus you may need to use a FR threaded top nut.
Your slightly pricier fall-back: have a skilled repair-ist splice on a new steerer on the old fork/steerer and then cut it for the HS (plus spacers) of your choice, you can even go with ISO/Brit threading if you do this. I'd reco Bernie Mikkelsen in Alameda for this repair, but a long drive if you're in Pasadena/SoCal.