Spring Tuxedo

Wearing a Spring Tuxedo meets half the requirement for Blushing Bride. The other player character needs to be wearing an Elegant Dress.

Source
Both items may be found in Brightly Colored Eggs during Noblegarden; finding both items in eggs grants Sunday's Finest.

They may also be purchased from Noblegarden Vendors and  Noblegarden Merchants during the event; although getting them this way does not work for Sundays Finest, they do work for Blushing Bride.