When me and my father went to Belgium, we bought a fishing rod pole :P It was quite thick and durable, we held the Mclaren Flag, Union Jack and Welsh flag on it, and it survived and could even be clearly seen on the on board TV cameras around Pouhon.
It was good because it retracted and we tied the flags on with zipties, so we took it back to the campsite every night and put it back up. In hindsight we could have kept them on, but we had to pass under a tunnel to leave the track and thats very difficult with that size a flag pole. Another neat trick is we went General Admission, and we brought 2 chairs to the track which we tied it to, seemed to do the trick, saved hacking them into the ground somewhere.