Reliable source of Stolen Correspondence?

Do any of the Unfinished Business storylets give that particular item up? If not, is there another way to reliable get a sizable amount of it, besides sinking echoes?

There is an Unfinished Business source for it, in Spite. It takes 2 actions, and has a nice Rare Success.

Yes. Try the Unfinished Business in Spite and mug a courier.

Thanks! :)