Thom Hogan (www.bythom.com) has commented at length on Nikon no longer selling parts. It is a new company policy and a bad one. You shouldn't have to return a lens for a situation such as yours.IMO this policy will backfire as it provides an incentive for all sorts of people to start manufacturing tripod mounting colors, lens caps. etc.
And this from Shakespeare:
"Neither a borrower nor a lender be".
Years ago I loaned a Nikon body to a colloeague who promptly dropped it out of a helicopter while aloft 50 ft. It has the dent to this day although still works perfectly. Taught me a lesson:~