Oh, yes.
I could build another F-122 from the parts I have on hand, if I only had another spacebar.
The spacebar is the same size as the M, but the F wire is considerably thinner.
I do not think that it would be hard to fabricate a more generous tab and epoxy it to the plate to accommodate the M wire. I have considered bending a "Z" shaped piece of wire, such as a 1cm section from a large paper clip. There is little pressure on the tab, it would not have to be overly strong (the stock press-fit plastic ones certainly aren't).
Wondering about a compatible spacebar is another reason that I have wanted to get my hands on one of those very early M-122s.