Other than in super rare cases (ie the item is valued at over 250K+) they no longer write stand alone policies for jewelry. Unless that has changed back within the last month or so.
I just insured my ring with Jewelers Mutual yesterday. Agent is Jennifer Holewinski and she can be reached at 888-884-2424 ext. 2377 also she answers emails efficiently. I sent her 2 yesterday and heard back within an hour. Her email is [email protected] I have heard great things about this company on this site.