Can I deduct a charitable donation of a single group of items worth >$5000 if I no longer have access to the items to get them appraised? Have receipt, no appraisal.

No.  You would need to have the appraiser and a financially responsible office from the charity sign a copy of form 8283 that describes the donation, which you mail to the IRS after e-filing.  Without an appraisal, the most you can claim is $5000.