NEW YORK — Brooke Shields returns to Broadway next month, taking over the leading role in “Wonderful Town” from Donna Murphy. Shields begins perfs Sept. 28.The model and actress, best known for her TV series “Suddenly Susan,” has appeared on Broadway in “Cabaret” and “Grease!” Latter show was produced by Barry and Fran Weissler, the producers of “Wonderful Town.” Revival of the musical comedy opened in November to some of the best reviews of last season but has never set the B.O. on fire. Murphy has earned some bad press for her frequent absences. Show has been doing middling B.O. for most of its run: Last week it earned just $350,000. However, the production, a slightly expanded version of the concert version presented at Encores!, does not have high running costs.