What cable can I buy to connect my camera to my iPod Touch?

When I take pictures with my normal camera, it takes a while to put the memory card in the computer, then photostream the photos to your iDevice. I tried searching online for some sort of cable you can buy that lets you connect your camera to your iPhone/iTouch. You know, just a camera cable that can connect to an iPhone. I didn't get any results online and I thought maybe someone knows where I can buy the cable (if it exists).