Green’s Dictionary of Slang

sussies n.

suspenders.

[Scot]I. Welsh Filth 305: She opens her coat, exposing the black bra, split-crotch panties, stockings and sussies. Phoah!
[Scot]T. Black Ringer [ebook] n.p.: I take a sketch at the legs , black stockings all the way up to what looks like sussie-tops peeking beneath the wee short skirt.