Hamilton Tool & Supply in Beaverkill Falls, PA had the Vertex indexing plates, and IIRC they also listed the tables. Do check that the one you're actually getting is Taiwan-made, though; manufacturers in that part of the world tend to outsource stuff to the mainland, with, shall we say, less than spectacular results.
BTW at the time I got mine, several years back, Penn told me they'd had trouble getting Vertex rotabs, and as a result, were carrying a brand from India -- "Baron" I think. I have no idea what their quality is like.