You've had a couple of good sources for the gutters recommended, but remember there also needs to be a vertical downspout, and you have a "free" source at your workbench. The round plastic sprews from almost any kit will work great. Trim the flash, cut to length, paint as appropriate and you have a very representative downspout. Some kits may also have sprews that are of a shape that might work for the gutters themselves.
Mike
Cool. Yeah, Pikestuff has lots of little detail things like that. I've got their highway guard rails. I think they really add a nice touch.
It's good to know that when you need an answer like this, some guy with his mind in the gutter will show up.
It takes an iron man to play with a toy iron horse.
http://www.walthers.com/exec/productinfo/541-3001 is one source. go to www.Walthers.com and enter gutters in the search box. Buy the paper catalog & be amazed at the detail stuff that's out there!!
You could use styrene C-channel shapes, or half-round rods. The rods, unfortunately, would be flat on top, not grooved. The C-channel has a rectangular cross-section. You could sand the outside edges round. Evergreen and Plastruct make these.
Most of the ones I have worked with are vinyl plastic. Some of the Walthers kits, such as their Santa Fe Adobe style Depot and add-on freight house, come with rain gutters, but I have never seen them sold separately.
If anyone makes them, the most likely would be Plastruct or Evergreen Models, but a Google search turned up only building kits from the likes of Model Power or Atlas that included rain gutters.
The Walthers 2008 HO scale catalog has no listing for rain gutters.
What is being used for building rain gutters in HO?
Richard