Gee, I ended up replacing the entire PTT unit on my '93 Merc, with a new unit. Price was mid $900.
e-BAY will have used units for sale, as well. The only non-OEM was a CMC brand PTT unit. I never used one...
Yes, $900 is a bit, however, I needed a new tilt cylinder and they were either N/A or avail in a few places for $800. It seemed to make sense to buy a new unit.
My research seemed to indicate that the PTT units were routinely replaced by professional mechanics, due to the small price differential between repair and replacement.
Used units were $250 and up on e-BAY. However, one could not tell the condition of them, over the web.