What are some available custom chassis machining services available online for your typical hobbyist? I have not been successful in finding one, primarily because I don't know what the correct terminology is.
To clarify, I would like to design the parts for a small robot (no larger than 5x5x5 in.) in SolidWorks or CAD and have them machined in a light but durable plastic material.
They are expensive, but focused on the one-off prototype. I would also try a local trade school. I did that many years ago and only had to pay for materials.
Try looking on a site like Hobby Machinist and see if you can find someone interested in doing your one offs for a reasonable fee. I have a mill and two lathes so I do that kind of stuff quite frequently. It does kind of fit with the whole hobbiest/machinist/robotocist ideal pretty good. If I were well enough I would be glad to fo it for you, but my health has not been good and I have not been out to the shop much at all lately either.