Search for Robertson screws
I have used Bolt Depot. They have a lot of slotted screws in an assortment of materials.
https://boltdepot.com/Catalog-Tabs?...hQYgqI5I6izrRCK0zKPslQpyi2pH9WicaAiPeEALw_wcB
I own an early 1928 tudor and have purchased many parts from Dixie Upholstery. They have packages already assembled containing screws etc. for the various Canadian model a bodies. Gene and helpers are always willing to give advise.
Dave
After establishing a collection of Robertson screws, I discovered my Australian Tourer (Phaeton) didn't use Robertson screws. Sigh...
What makes you think it didn't use them?
Only Canadian cars and trucks used Robertson screws and hardware
The Australian Ford factory was owned by Ford of Canada.