Make a CAD model of it, then send that file to get it prototyped. I've used http://www.redeyeondemand.com and http://www.quickparts.com before; didn't have any extreme experiences with either of them (either good or bad).
A paper model is a good first step because the materials are cheap and easy to work with. Modeling clay, etc are good second steps.
For a first timer CAD modeling is a lot of investment, but it's definitely where you want to be. You can buy a desktop 3D printer now for $5k (http://www.desktopfactory.com/our_product/).
To tell you the truth, I learned CAD while designing cases for the electronic products in my previous startup, and it took literally weeks; not more than a month. To get started, I went through several steps of the SolidWorks tutorial, then started over on things I wanted to make. The easiest package for me was SolidWorks, although the latest versions of AutoCAD are just as easy. While SketchUp is easy, it's awkward to to CAD-y things like draw a line and simultaneously specify its length (at least, that was the case when I tried it a year ago).
In less than a week you should be able to make useful stuff. These are the kinds of programs, though, that it is easy to forget much of what you learn after you don't use them for a while.
Rhino has an evaluation version which is limited to 25 saves. They have very good tutorials, extensive documentation and an amazingly helpful support team and user group.
It isn't that hard although the pro packages can be very intimidating. It's more a matter of time commitment than conceptual difficulty. Sketchup is pretty easy, I'd start there.
For a first timer CAD modeling is a lot of investment, but it's definitely where you want to be. You can buy a desktop 3D printer now for $5k (http://www.desktopfactory.com/our_product/).