You mean squadron emblems with DC-3s on them?
I'd try the biggest local library you can find. You might even try one with a government documents section. Do some research on old squadrons and try and locate some old squadron emblems with DC-3s on them. Borrow the book and scan in the image. Then, take the image to Kinkos and they will be able to print it on bumper sticker paper for you.
I think it would be really difficult to find such a thing and you're probably going to have to make it yourself.