This is one of the best links for finding a pumpkin.
Ownster.com
They throw craigs list, Ebay and a few others in your search results. This is how I found mine.
Also don’t just try to find the pumpkin. Rolling chassis‘ are also a source. Just ask for the pumpkin. That’s what I did. Find someone selling a frame or part of a truck. And don’t let anyone here kid you. They are hard to find unless your in the north.
Don