I have one in excellent condition! I bought it new many years ago. I think I still have manual etc. I also have some copies of the yamaha newsletter/magazine called 'Aftertouch', some of which have articles and notes about the CX5M.
I haven't used mine much lately, but I have some good patches. I'd be interested in finding a floppy drive (FD-03 was it?), since I have had to back up everything to cassette tape, which is a huge pain.
I wish you luck in getting your site going. Let me know if you want copies of some of this stuff (or if you have ideas of how we could post patch files. ) I suppose I could scan some things etc., but I don't have a lot of time for such hobbies.