We met the folks at A&G engraving (super nice!) at the printer's fair because they were right by us. They do a whole plethora of things including magnesium and copper blocks. The letterpress pieces they had in their booth that were done with their plates were fabulous. We still use magnesium plates (in addition to polymer) so it is nice to find a west coast source! Here's a scan of a typical price set. 
