There is a new brand, Rey Fernando, that is available at the better small stores (J. Webb, Wine Ink, Metrovino) etc. I think it is significantly better than Alvear or Harvey's. Harvey's isn't even sold in Spain, as the Spaniards won't drink it! They also have a manzanilla, fino, oloroso and pedro ximenez, all of which I have tried and love! We have been drinking sherry for years, and have found this to be much better than what has typically available. Salud!
Try the search here http://www.liquorconnect.com
It will list stores that have ordered it but you will have to contact the individual stores to ascertain if they have it in stock.
Highlander Wine & Spirits has one bottle in stock according to their online inventory but maybe there are ones in locations nearer to you (wherever that is).