Have you thought about just rebuilding the LU yourself? Just buy a new pinion, dog clutch, or whatever from Yamaha for a couple hundred bucks and do it in your garage. Lots of videos on Youtube for this. It's not hard with the right tools (lower bearing carrier puller, mainly) and some new seals/orings.
I can also dig up some contacts from Florida and Massachusetts that sell used LU's -- they have a healthy used market there. LMK.