Which widget can show posts from a post's category?

Hello,
I'm searching for a widget that can be displayed in article view.
It would show the last N posts from the category of the post that the visitor is currently viewing.
(A post is assigned to one category only)

I've search for 2+ hours and cannot find a simple solution for this.
(There is a hardcoded way which I implemented, but its confusing for my users...)
Thx.

PeterB