Amazon.com: ZHUOMINGJIA 2 Sets 3/4 In PVC Bulkhead Fitting For Rain Barrels, Aquariums, Water Tanks And Ponds Dark Gray(2pcs Bulkhead Adapter And 2pcs Plugs+2pcs Water Pipe Connector) (3/4 IN, 2) : Patio,
Proline Series 3/4-in x 3/4-in Threaded Female Adapter Union Fitting in the Brass Fittings department at Lowes.com