Jim Quashnock asked about #1 and #2 cut tacks [211010 MMD]. I have
also had a problem finding them! So, that prompted an Internet search
(haven't searched for them for awhile). I came upon this very useful
site: https://dbgurney.com/collections/upholstery-carpet 

It looks like they are using machinery that probably made the original
tacks you have in your piano!

Their FAQ is pretty useful -- I learned why they are called #1, #2, etc.
See https://dbgurney.com/pages/faq 

Ann Donoghue