Where would i find a ph tester for making homemade vinegar?

i am wanting to try to make my own homemade apple cider vinager. Since My wifes family has a abunt supply of apple trees.But i know when i buy it from the store it reads on the label reduced to 5% acidticty. But where would i go and look or where would i find a tester to find out the PH or Acidticty if my own homemade vinager to make sure it is the same as what we consum for the store. Your help would be greatly appreciated