Camp Suki (formerly in E. Rodriguez)
now located at #88 4th Street, New Manila, Quezon City
Call them at # +63 2 7250819
The costume shop has been around for years and it has been in the arsenal of local production designers. They have a wide range of costumes and various themes. You need to make a deposit of 1000 pesos and the rental piece costs 700 pesos per day.
If you're creative enough, make one, design your wardrobe its much more fun! Design it then have a tailor in your neignborhood make it for you, I think that's a good alternative. Or hit the ukay-ukay stands (thrift stores)in Bambang for the vintage groove or the discarded wedding gowns.
There's also a costume and Filipiniana store in Villalobos street in Quiapo, but the selection is very limited and the generic kind.
If you have student connections, the university theater departments have Shakespearean period pieces, you can sneak out overnight.