Also, building a suitable crossover with new components (while searching for the vintage stuff) should be relatively inexpensive and easy.
Another thought, given JRH has documented PWK's upgrade to University SAHF mid and t-4401 tweeter along with values for the crossover, why not build the three way for now? It should work with your existing horn, sound great with the new crossover and be faithful to known documented 3 way "provenance" as owned by Major Armstrong.
Upgrading was common and encouraged at the time.
I may have a SAHF and 4401 you can have for the cost of shipping.
You can throw in a K-33 woofer (from Crites or otherwise) to get excellent bass (I have compared both and while there is a difference, it is not night and day) while searching (and saving) for a proper Stephens Trusonic woofer.
You would have a super mono speaker to enjoy in short order.
Just my 2 cents.