Synonyms for Chance on:

n.

map, come-on, stumble across, dig out, trace, track down, locate. chance on (noun)
chance upon, attain, come across, come upon, strike, happen upon, fall upon, discover, light upon.

v.

meet (verb)
strike, come across.
possession (verb)
chance upon, attain, come across, come upon, strike, happen upon, fall upon, discover, light upon.