I just did a lengthy search and came across this. It's rather pricey, but it looks to be strong and the dimensions are adequate (assuming Sondor's and QuietKat's specs are correct). Nothing else I found was big enough, particularly in thickness.
Closer to 70 lbs. I’m thinking a bag would make it easier to move by providing a top handle. I also plan to store it without the battery in it, which will save 7 lbs or so.
It's intended to hang off the back of your roof rack, but those straps looks like they'd make good handles. It's short by 1" in one dimension but makes up for it by being soft sided and oversized in the other two dimensions, not to mention that the folded bike isn't a rectangular solid.