What I thought was easy to find, I have to say that I didn't come up with much
I found this at Pelican (scroll down):
http://www.pelicanparts.com/catalog/SuperC..._TRANSM_pg6.htmAt this price I hope it's metal.
I think I remember paying about $15 or $25 for my plastic one a few years back on the samba or something.
Good luck with your project.