Coletti
Coletti's percolators are built for exactly the plastic-free buyer: the entire brew path - pot, stem, basket, and spreader - is 18/8 food-grade stainless steel, with no plastic and no aluminum in any coffee-contact part. The non-steel parts are a hardwood handle and a glass lid knob, both non-plastic, which makes the percolators effectively plastic- and silicone-free.
How clear are their specs?
States 18/8 food-grade stainless brew path with wood handle and glass knob; materials are clearly disclosed on the product pages.