This weekend (during Arisia setup) they are open Thursday 7:30am - 4:30pm; Friday 7:30am - 3pm, and Sat. 9am - 1pm.
NOTE: They will accept an order on the phone and send it immediately via currier for "a small charge," according to their website. Their number is 617.330.1422
In case you're curious: no, I have no financial ties with these guys, they're just an awesome hardware and theater supply company in South Boston. Not that anyone has any free time, but if, hypothetically, you did, and you're not from the area, I would highly recommend a field trip over there. (Tell 'em topper sent you, if you feel like chatting).
From their website: Backstage stocks a full line of Rosco products, Artists' Choice paints and Sculpt or Coat, Tapes (gaff, spike, etc.), Fabrics, Stage Hardware, Trickline, Scatter Snow, Wardrobe Racks, Crowd Control Ropes, Hampers and just regular hardware stuff. We service universities, high schools, television studios, film companies, special event and display companies, photographers, the fishing industry and many local businesses. Located on Boston's busy waterfront, our store is decorated with murals and artwork painted by some of Boston's leading scenic designers. Stop by and visit!