http://www.ebay.com/itm/Alita-Air-Pumps-airpumps-AL-6A-AL-15A-AL-40-AL-60-AL-80-AL-100-etc-etc-/330740199172?pt=LH_DefaultDomain_0&var=&hash=item4d01a6ef04#ht_2355wt_1034
They have various sizes to suit your needs i personally use the al-100 for 16 water farm units for both drip & airstone in each.