I have posted in the past that, if you want original slotted nickel-
plated screws, American Piano Supply Screw Division is still open.
Schaff bought American Piano Supply but not the manufacturing or screw
division of American.  It is now known as John Schadler and Sons.

Their phone number is 866-842-4266.  I fax my orders, with credit card
information, to them at 973-777-0481.  Most of the time they get the
order right.

They also have plain steel and brass-plated screws, as well as solid
brass screws.   Andy usually answers the phone.  There is a $25 minimum
order, and they prefer to deal with piano tuners or at least a person
who knows what he wants.

Schaff also stocks more screws than their catalog shows.

Don Teach
Shreveport Music