OK. It seems like there are two concerns here.

First, can the pumpkin pass the vagaries of the TSA? Well, you grow pumpkins so your investment in a 20lb pumpkin can't be much, right? So it's not a big loss if said pumpkin gets chucked.(Punkin' chunkin' anyone?).

Second, you obviously have pumpkins in assorted shapes and sizes. Grab a couple and see what fits in your carryon or even a canvas tote bag.

Problem solved. Whoo-hoo!