L.B.
Most reputable dry cleaners also have tailoring services. I would call around and see who will do bridesmaid dresses.
My husband just had some tailoring done by the new dry cleaner in Eagle on Route 100 in the new shopping center beside Dunkin Donuts. I'm sorry, I don't know the name of the place. He was very happy with their work and their prices.
There is also a woman in Exton (near Walmart) who has been doing tailoring for years. The business name is Maridadi. She altered my wedding dress and I don't recall it being overly expensive. Here is her website. http://www.maridadisewing.com/ Just not sure how busy she is this time of year.
Good luck.