I found a company (ExOne) that can 3D print them out of 316 Stainless/Bronze for about $100 each. I ordered one without any protective coating and will use it to run a corrosion test with hot saltwater with some SS screws attached
but the production/sales engineer I talked to thinks it should do fine. I should get it in a week or so.
Printing metal is much different than plastic. The technology ExOne uses is called binder-jet - basically they use finely powdered 316SS covered with a binder to print the part in ~.003" layers. Then they do a vacuum infusion in a furnace where bronze fills the voids and displaces the binder. Net result is 60%SS and 40% Bronze (bimetalic, not an alloy). Then they do blast and polishing - I ordered a grit-tumbled polished finish.
They also offer what is called their 'Navy' coating; a baked on clear lacquer coating they developed for the US Navy - he thinks the finish should last 10-15 years in this application. Probably a good idea but I want to test the unprotected metal first.
I looked into doing them with the aluminum (Thx Doug - good connection) but am pretty concerned about corrosion on that when it gets scratched, around the bolts, and on the back side where it will stay wet. These things are too much of a PITA to be replacing regularly. For a lower-cost option I think we can get plastic 3D prints but I love the look of the one I had printed out of 420SS/Br - unfortunately 420 will get surface rust. One interesting thing is that the 3D printed metal parts shrink non-linearly so the size needs to be scaled up a couple of percent - I am trying 1.7% on this one based on the shrinkage of the 420SS/Br one.