I've asked that a few times in response to comments such as yours, and no one has ever come up with one.
You understand correctly, I think.
Wilson's famous letter, 'What I Didn't Find in Africa', included the phrases 'I was informed by officials at the Central Intelligence Agency that Vice President Dick Cheney's office had questions about a particular intelligence report' and 'The agency officials asked if I would travel to Niger to check out the story'.
I'd say the 'officials' were his wife and someone like her administrative assistant, who seized an opportunity to grind a political axe. The outcome of his trip seems to have been determined before he left.
Here's where the idea that Cheney sent him got started, by Wilson himself:
http://www.globalpolicy.org/security/issues/iraq/unmovic/2003/0506missing.htm
and it is in fact repeated in this WaPo article (see my excerpts in post #63).
Wilson was the source for Kristof's May article.
The 9/11 commission report shows clearly that he was sent at the recommendation of his wife, a CIA employee.
The media chooses to ignore facts that don't fit their agenda, but the info is in the report.
Check out the Kristof column, which uses Wilson as an anonymous source.
It's true that Wilson never expressly claimed that Cheney sent him. However, he was evidently happy to leave that impression with his interlocutors and let them suggest that he (Wilson) was on a mission from Cheney.