So that looks like the Lionel 5903-1.
I am not aware of a "generic" term/name for on-off switch that can be activated either momentary or toggle. Electrically speaking this is just 2 SPST switches in parallel. Given the somewhat large footprint, I'd think the economical and practical route is to individually find a suitably sized momentary SPST and slide/toggle SPST and pair them.