First: try searching for "bongs." (At the time of writing we notice that the selection is rather small and also included hookahs in the search).
Second: Don't try searching for water pipes because you will actually get results for garden hoses instead.
Unfortunately, it we could not really get good results to come up when trying to find an Amazon bong, but hey! If you want to buy a bong with fast 1 week shipping (for the USA) you can always check out the collection at Rockygreenking.com.