The best one i have is made by Moultry. My buddy has a Reconyx which is a lot better than mine, but also a LOT more expensive.
Acturley i'm not sure that a trail cam would be the best solution for your purpose. The infrared cams still make a light ( not a flash) when they are taking pictures and that would reveal your cam.
There are a lot of better solutions on the market when you are talking about spycams.
I have some at my bussines that are recording video at night without any light at all. They only record when something is moving. A lot have happened since i bought them app. 10 years ago.
Today they are wireless, not very big, dont need a recorder caused the memorycards, and best of all they are inexpensive.
Now i don't know where you are going to use it or if there is acces to electricity but i would be very surpriced if you can't get cameras that works on batteries that would fit your purpose.