Where can I find a good wading pool for my dog?

You can use a hard plastic child's pool from Wal-Mart or K Mart. That'a what I have always used.

I got a good deal at Costco, or you could also try Sam's Club, as well as what was mentioned above.

We use a large pool that has a blow up ring around the outside... it can be as deep or shallow as you want as the inflatable ring rises as you put the water in depending on the size of your dog (or your kids :) )
They are available at Kmart and our 15 foot pool cost $115