Good and cheap can be an oxymoron. There's tons of stock footage out there to be had but it can be very spendy. A couple of places to start for buyout might be Artbeats (I know they have animals), and possibly DigitalJuice.
And does this footage need to be animals in the wild? If not, go to your local zoo...... Even most zoo's now have environments set up where you could capture some animals "in the wild.." http://naturestockshots.com/