I don't see why it couldn't be neuropathy related. Since you've exhausted other avenues, a neurologist would be worth a shot.
My polyneuropathy mainly causes numbness below the knee and and electric pains in my feet. It is also accompanied by itching in my feet.
Have you tried topicals as others have suggested?
My foot itching responds well to topical lidocaine, or if milder, trolamine preparations like Aspercreme or Sarna.