Many cheap/consumer devices let you disable some automatic adjustment, but rarely do they let you disable everything. For example, I've seen webcams that can fix the white balance but have automatic saturation adjustment that can't be turned off.

The cheap option that comes to mind would be an old and/or second hand Canon PowerShot capable of running CHDK firmware. Ask friends and family; you'd probably be able to score one free from a dusty cupboard draw.