In 1917, my catalogs show the following pads being sold.

Silvers

American Silvers , also called Grieb and Goodrich [1918] These looked like the Silvers but had sort of an ochre colored line between the black base and red rubber.

Huntley sponge, like Jostam sponge of a year later.

Jostam Anti Flinch

All of these would be a proper "period pad" for you.

http://www.bakercollectors.com/