Learning Resources Toys

I make a lesson for 23 children and I want them to learn group of vertebrates and invertebrates.

A bit like http://www.amazon.com/Learning-Resources ...
But I need to mammals, insects, jellyfish, reptiles, amphibians, arthopods, etc.

And preferably under $ 20-30?

I found these at Walmart and Dollar Tree .. but not all the time. Stores offering of this course teachers have a little thing, like specialty toy stores, but they can be expensive. I saw the "lots" on eBay. You can try this approach.
Here is a much smaller ocean.
http://cgi.ebay.com/12-vinyl-OCEAN-ANIMA ...

Some other ideas ..
http://search.ebay.com/search/search.dll ...

Try your local dollar store. This is a great source of small plastic toys.