I'm a flamenco guitarist so I'm in "tune" with the flamenco music sources. :-) I know there's more to Spanish music than just flamenco, but this is what I know best...
Online you can visit
El Flamenco Vive which is an actual store in Madrid. Another one is
Flamenco World which also has a store in Madrid.
If you prefer to order from a store in the USA, try
Flamenco Connection which is a mail order business based in Falls Church, Virginia.
Hope this helps.