No no no. Don't spend your money on gimmicks. Before you leave home run Wolfbane (
www.wolfbane.com) and find out which transmitters serve the location you are visiting and make a note of their bearings. When you get to site first use your eyes and look where aerials on nearby properties are pointing - and by properties I mean houses, not caravans - and especially note the polarity, vertical or horizontal. Use those as a guide and bear in mind the directions you got from Wolfbane, then all should be well.
Note that TV aerials are not critical on direction like a sat dish. Most of the aerials you are likely to have on a caravan site will have a beamwidth (acceptance angle if you like) in excess of +/- 10 deg so the absolute direction in which you point it is not so important.