You don't want anything in a bag any longer than you have to. Your clown will be fine a couple days (or forever) without an anemone, so wait until you have a whole day to devote to getting another anemone so you have plenty of time to acclimate, and are not in a rush. Heaven forbid you wreck your car while rushing to get home or something.
Anemones do best (in the ocean ) in mature tanks, so if you already have one that is not doing well I would hold off and find out why before possibly losing #2 to the same reason.