My nephew got this for Christmas last year and my son couldn't keep his hands off of it, so with an extra gift card that I had I went to Target and bought one for him. It is from National Wildlife Federation here is the LINK.It is a view master too, so you buy the little books with the cards in it and let them explore. The best part is that they are 3D and they come with an information booklet with several disks in them.
If you have a little one who loves stuff like this I HIGHLY RECOMMEND this product. They even have a disney set of cartridges too!
Oh did I mention that if you didn't want it to be a view master it has a switch on it so it becomes actual binoculars? SWEET!