He will join the team in Milwaukee.
Flores is hitting .341 with a .376 OBP in 93 plate appearances since July 1. He has eight home runs and 28 RBI over 21 games, and recently had a 23-game hitting streak snapped.
To make room for Flores on the roster, the Mets optioned Kirk Nieuwenhuis to Triple-A Las Vegas. He was hitting .179 with a .294 OBP over 34 plate appearances since July 1.
Ruben Tejada was hit in the helmet by a fastball during Wednesday's game, but was later cleared by the medical staff and traveled with the team to Milwaukee. Eric Campbell took over at shortstop for Tejada.