Bountiful Bazaar is one of the possible Super Kupowers granted after all 11 Mog Tablets have been found and returned to the Explorer Moogle in Ru'Lude Gardens.
While "Bountiful Bazaar" is in effect, all Regional Merchants in San d'Oria, Bastok, and Windurst simultaneously open for business, regardless of current regional controls.
For a list of all merchants that open shop during "Bountiful Bazaar," see Regional Merchants.