I expect you're saying that you can vouch for the accuracy of the quote, but not necessarily whether Feynman said it? Actually, I'm skeptical about whether he said it.
Absolutely. That's the thing -- I've read a lot of Feynman's stuff and stuff about Feynman, and that quote rings no bells.
- QED, The Strange Theory of Light and Matter -- Richard Feynman
- Surely Your Joking, Mr. Feynman! -- Richard Feynman
- What Do You Care What Other People Think? -- Richard Feynman
- Genius, The Life and Science of Richard Feynman [1995] -- James Gleick
- Feynman's Lost Lecture [1996]
- The Meaning of It All, Thoughts of a Citizen-Scientist [1998] -- Richard P. Feynman (A collection of three previously unpublished public lectures given by Feynman in 1963.)
- Feynman's rainbow: a search for beauty in physics and in life [2003] -- Leonard Mlodinow
Of course, the quote is all over the internet as being attributed to him -- on instagram and facebook, etc., etc., but none of those provide where they got that information from -- what book, what person heard him say it, what video? I'd be happy if confirmation was brought forward, but I haven't seen it yet.