Where did Littlefinger get the dagger?

mot Valyrian steel weapons are heirlooms of great houses that have been owned by the family for generations. Tywin was one of the richest men in Westeros and has been unsuccessful in trying to buy on from impoverished houses.
Littlefinger isn't part of a great house. He was I suppose almost the founder of what would have been House Baelish. So it can't be his ancestral weapon.

Stolen maybe? I know the Boltons passes down a flaying knife, could that dagger have been it if he'd paid someone to steal it?