Okay, I finally get to add to this conversation. The shovel is definitely a modified version of a Ames folding E-Tool (Entrenching Tool) from the period. Actually they haven't changed much over the years, except for the handle, and more recently the addition of some serration on some of the edges. What I've been able to see of the shovel it looks just like the one I was issued in USMC, except for the repo they made does not have the actual mounting bracket that the handle was attached to. The real thing will work, the mount will just look a bit different. I have a second option too, but I really think the design used the folding E-tool, because it was and is very common and would have been in every house after WWII.
The second option is also a WWII Ames E-Tool, but it was the non-folding type, and not used nearly as much as the folding. The advantage, this one does not have the bracket to deal with, but to make it look like the one on the jet pack would require shortening and then cutting into the metal sleeve that the wood handle fits into, cutting out the sides, and just leaving a front and back, and then hammering both of those flat so that you have the "tabs" as in the movie versions.
So based on the Americana (which is very Disney) of the pieces used in this prop (Electrolux, Schwinn, several American motorcycle and auto companies, and what appears to be a fictitious fire extinguisher company, even called American) I will highly suspect that the shovel head (design at least) was a nod to our WWII heroes. So, that's my two cents. I plan on using the folding one, like this:
Then drilling out the bracket, plugging the holes and then reattaching the bracket at the top edge of the shovel to the two flat pieces to attach with. Hope that all makes sense, and that I've been able to help you in some small way for all the help and inspiration I've absorbed from this very supportive and helpful group of prop nerds. Thanks all.