The donor shifter boot is gone since last winter. I am stupid.
The one FFR supplied has a very weird angled base, like a distorted hexagone or something with none of the side the same length. Maybe I could cut the base, get rid of the metal pins making the base solid, use what's left and enlarge the hole (meant for a shifter rod, not an ebrake). That's an option, yes! I have a few options now, so I won't be concerned any more about that.