Is there a good site where I can buy a few night vision camera which I could leave running over the course of the night?

I just Google shopped "night vision cameras" and there seem to be plenty of affordable ones:

https://www.google.com/search?q=nightvision+camera&ie=utf-8&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&channel=fflb&gfe_rd=ctrl&ei=tr4sU8SsN8rR8ge_9IHIBw&gws_rd=cr#channel=fflb&q=nightvision+camera&rls=org.mozilla:en-US:official&tbm=shop

These don't look too expensive and work for night-time

http://www.tmart.com/30-IR-LED-Night-Vision-Secuity-CCTV-Camera-with-Waterproof-Function_p121020.html?cc=USD

Are you looking for something specific? Does it need to attach to the wall or something?? What are you planning with it anyway?