Has anyone ever seen one of these? http://37plyguy.com/pt50pics/parts/37OMPT50.jpg
I sure haven't.
When it comes to the Manual, I would contact Andy Weimann who advertises in the "Plymouth Bulletin" first then if he doesn't have it, go online to "Hemmings Motor News" and check out literature vendors, Walter Smith comes to mind, very good to deal with. I go my Owner's Manual for my 1940 Plymouth P10 Business coupe 20 some odd years ago at a car show, but have seen them on ebay also, so you might want to check out ebay.
Hope this helps,
Bob