I've got a couple of Motor Drive MF units for the original F-1 and F-1n (but not the F-1N aka F-1 New). They are both the style with the two lock swivels on the battery door, which I find to be the more secure design. They both still have the original "soft touch" mushroom button on the trigger. One of them is in nearly flawless condition because it was always my spare. That one has always had the issue, in the 30 years I've owned it, that if you don't use it for a long time sometimes it acts dead...but a sharp rap to the battery compartment brings it back to life. I have no idea what that is. Both of them have very clean battery compartments and no corrosion, but maybe the one is just haunted.
I'm asking $150 each, but that includes shipping anywhere in the world.
The pristine but occasionally balky one:
The mildly scuffy but non-flaky one: