Searching JW on Ebay will take you hours and hours... but together our members could point out to each other the more interesting finds. If this post gets some reaction, I might even be pinned by our moderators...?
So I'll jump start you with this one:
that's a great parody on The Alamo in MAD MAGAZINE, 1961, with great artwork by one of MAD's very best, Mort Drucker. You'll notice that in those early days they tried to be careful: The name John Wayne is never spelled out - it's John WAYDE. Cowards!!!
(of course, I'm only going to point out JW stuff that I'm not bidding on myself. I'm not stupid, y'know!)