Check this link out - lists all the spring consignment sales by date. http://www.our-kids.com/static/?f=dcspringconsignment
You might be able to find a baby gate. Would recommend getting there before the sale even starts - there's usually a line out the door and all the good stuff gets snatched up quickly.
There's always Craigs List. DH and I got new baby gates (really nice ones, sort of $$) and about a week later my mom decided to get the same ones for her house (for her dogs - to block them in the family room) and she was patient and haunted CL. She got hers for about 1/4 of the price we paid new.
She also bought a bunch of Super Yard pieces - however many it comes with plus extra pieces - same thing, to block her dogs when my parents leave the house. Again, she got them for a steal on CL. (we bought ours new... gees, you'd think I'd have learned the lesson!)