She was stumped for ideas on what to do for her friend's birthday.
stumped on
Frequency:
60
%
He was stumped on how to fix the broken car engine.
stumped with
Frequency:
50
%
They were stumped with the decision of where to go on vacation.
Idiomatic Expressions for stumped
Phrase: stumped by a problem
Meaning: unable to solve a problem; confused or perplexed by a difficult situation
Usage: He was stumped by the math question and couldn't figure out the answer.