I don't know of any independent, but Cross Country BMW in Metuchen has been great to me. I too do all my own wrenching but the few items they looked at my K16 for me under warranty were handled with the greatest of care and professionalism. if I decide not to do the 18000 mile service these are the guys I'll have to it.
1982 Honda CB900F
2011 Triumph Tiger 800
2018 BMW K1600GTL
2012 Triumph Thunderbird 1600 (gone)