Brent,
I don't think I have ever seen galvanized wood screws (I assume you are concerned with wood screws) in my work on model A's. Most are unfinished or nickel plated. Fastenal is where I have purchased most of my fasteners. They have a large selection of slotted fasteners. The link below goes to their website.
Rusty Nelson
https://www.fastenal.com/product/fas...regation=Drive