You should be aware that if you use a "y" connector you risk zapping any electronics in the camera since the open switch voltages add.
If you're in the west loop area Helix(They're on the corner of Racine & Jackson) and were(are?) open Saturday. At one time they were good but have leaned digital.
Central camera on Wabash is in the loop but I don't know if they're open on Sat.
I believe they both have websites you could check hours on.