Hi jivewire,
Those brackets are made from kiln-dried, clear Western Red Cedar. Typically, smaller pieces are laminated together with exterior-grade wood glue, and then machined into the profiles we design. A good source for those is a company here in Minnesota - Architectural Louver Company. You can contact Curt Buehning at (612)250-1882, and he can manufacture and ship those for you if you wish. He recommends using either kiln-dried clear cedar or All Prime products, and applying an oil primer while the wood is still fresh - before they have weathered gray.
Cheers,

Thanks so much!