^^^^
@flintknapper beat me to it. I had the exact same thing happen to me as what happened to you a few years back. I bought as short as possible M8-1.25 bolt at a hardware store and an assortment of fender washers. I stacked a lock washer on the bolt first then an ascending diameter of fender washers underneath to back up the bolt head with the innermost washer being big enough to bump up against the lip and cover the diameter of the drive flange.
Once it was all fitted, I disassembled, cleaned threads and applied red threadlock to the bolt threads so that it wouldn't back out. Finally I cut out a plastic yogurt cup and used that on top of the contraption with some gorilla tape to keep water and dirt out as best as possible.
There was a good bit of play and clunk, but that setup got me home where the repair could be made and bought me enough time to source and receive parts. I checked it often to ensure it didn't work loose but the threadlock held solid. Good luck with your field fix and hope you make it safely to your destination.