While fishing through the dumpster of my local bike shop for the cardboard to do my layout, I came across a bunch of car-mount bike rack parts (from display models) that they were discarding.
It just so happens that one of the u-shaped armatures was the perfect width to serve as the rear swingarm. It provided enough clearance for the chain drive and a disc brake.
Another was slightly narrower, which perfectly suited the width of the front tire without chain drive or brake and therefore served perfectly as a front fork.
I was really lucky. I had some ideas for building these components, but didn't have to. I wold recommend visiting the atomiczombie.com website for suggestions on this if you can't work it out yourself.