I would suggest you try contacting his manager at:
Peter Asher
644 N. Doheny Dr
Los Angeles, CA 90069

I found a coin dealer who came across and bought an James Taylor autographed acoustic guitar and he is looking for a buyer who would appreciate it. Not sure what hebis asking for it but it is doubled verified authentic with both picture of signing and DNA (or something like that) certifiied. His email is investingifts@Gmail.com. Hope this is helpful.