Where to find fresh duck eggs?

I know you can find preserved / salted duck eggs fairly easily, but I'm not entirely sure where to find fresh duck eggs.

Is it possible, and if so, are there any recommendations within the greater Tokyo area?

Thanks!

(eta: I've tried most of the shops in Ameyoko, etc., to no avail. I do not have access to a duck and am not generally interested in eating things I find on the ground.)