Inflatable Mattress Where Can I Buy An Inflatable Mattress " Air Leak " Detector For A Very Small Leak ? See Detail.?

Where can I buy an inflatable mattress " air leak " detector for a very small leak ? See detail.? - inflatable mattress

I have a queen-size inflatable "high" mattress with a loss of lease that keeps our air even if I have to keep Manufacurer filled with built-in electric pump. Thouroughly I tried spraying them with water and soap - do not find the leak. The manufacturer says he intends to use the Wal-Mart or Target, but I seriously doubt they have the leak detector. Who knows exactly where I get one?