The back mudguard (Ok, fender

) came from a classic/custom shop in Melbourne. It's just a generic full length 6" wide thing. I trimmed it down, welded a few mounting tabs on, drilled holes, painted and there it is. Had to make some stays as well. They attach to the swingarm via the axle nuts.
This one
http://www.dimecitycycles.com/6-inch-wide-raw-steel-flat-front-or-rear-custom... is pretty similar, maybe a bit deeper on the sides. Other guys use a trailer fender, right?
I saw in another thread you asked about seats. FWIW the one on mine, and the brackets, I made from scratch. If you like I can explain how I went about it.