We've been looking to buy a birdbath this spring but haven't found anything beyond the generic ones sold at Lowes. HEB will usually have some this time of year but haven't so far.
I second going to either Moore Wild Birds or Fraziers in Hempstead. I got my tiered fountain from Fraziers about three years ago before Moore Wild Birds opened here in town. I highly recommend getting a fixture for birds that features running/recirculating water. Birds love the sound of running water for drinking and bathing.