The concert uniform for the NUCS is as follows:  

Men wear black tuxedo jackets, black bow ties, black pants (either tux pants or plain dress pants), black shoes (shined), black socks and white shirts.  The shirt could be a tux shirt or a plain white dress shirt. The NUCS has a few tux jackets to lend to men who may not have their own; men must provide their own bowties.

Women The chorus will lend each woman a long black skirt. The skirt must be returned after the performance. Each woman will wear a formal long-sleeved black blouse (you must purchase your own blouse), black formal (but comfortable) shoes, and black nylons.  

Tutti: Please, no strong perfume or flashy jewelry. And please shower and apply deodorant before the concert.

Keezers in Cambridge is a good place to buy (or rent) tuxedos.

Cousin's is in Connecticut, but you can buy tuxes and gowns on line.

Cheap Tux Dot Com is another on-line store.

Simco is another on-line store.

New Era Factory Outlet has good prices on tuxedos (800-875-4959).