Custom mechanics were mentioned. These guys do small series of mechanical parts, even as few as one. Their CAD software is easy to use and gives instant estimate of cost:

http://www.emachineshop.com/


The downside is that the CAD software is for Windows only. If you're not willing to use their software or learn CAD and machining basics, they also offer an hourly-rate design service.

I almost got to use their service for a project at work. Sadly, the project got cancelled, so I cannot give any real-world recommendations. I just thought to mention this interesting service concept.

Featured projects from customers and staff:

http://www.emachineshop.com/machine-...y/page338.html