I've never seen any....since my layout is in South Texas, we don't really have need of any.....but it's a great question and I'm looking forward to seeing some answers.
in theory, I would think the gutters could be represented by sorta-square styrene with a groove or even just a dark line to represent the open top. Edge-glueing a pair of L strips might be a bit tedious and I'm not sure you can find them small enough (4-6" in width after assembly). Round gutters would be easier from split round tubing but i don't see round gutters too often.
The downpipes would be easy using brass wire bent to fit and painted.