Electronic Boutique or Babbage/Software Etc might have them. Try Funcoland as well. (They have a larger Used selection though) Also try electronic superstores like the wizz, Best Buys, CompUSA and Circuit city. They bought tons of games that never sold, and sit on the shelves at rediculously low prices just waiting to be grabbed.
Oh and... get RR4, Sega GT isn't the best game (I have both, and Sega GT breaks down when you get high powered cars, because everything feels like an icy road with 900hp )
I still play Ridge Racer Type 4 because of its big line-up of cars... I want to see those cars in a 128-bit system... Is that Bleem hardware still available?