Most new renovation supply items come with Phillips head screws [1] which were designed in 1935.

For period homes slotted screws are generally the correct screws for hardware fittings.

Industrial Zebra has a range of original design cut (not rolled) brass and steel slotted screws for most applications which can be purchased in quantities of one or more.

[1] Henry F. Phillips created the Phillips Screw Company in Portland, Oregon in 1934 and the patent for the Phillips or cross head screw was granted in 1936