I haven't seen those kind of pedals in YEARS! We called them "Rat Trap" pedals.

You should get the alloy kind, that Dannoxyz showed in his reply.

As for *both* pedals falling off within minutes of each other, somehow I suspect vandalism.
Maybe precise "planned obsolesence"? These pedals were made in like, 1978, and the engineers designed them to both break at the same time...

You didn't spray WD40 on them by any chance , did you? Sometimes the WD40 melts the gummy grease that is holding things together.