Found a place that does different sized flag poles and will even make up a large flag of your own design.......
The poles come in 3m, 4m, 5m, 6m, 7m, 8m, 9m and the monster 10m size.
A 6m Telescopic Pole + 2 ground spike package comes in at £14.98 with 6 postage. Collapsed size 115cm and is 6 sections in side each other.
http://cgi.ebay.co.uk/6M-Telescopic-Pole-2-Ground-Spike...27b2624206
They will also make up a flag of your own design...personally I like the pirate one
http://cgi.ebay.co.uk/Skull-and-Crossbones-Prepare-Boar...27b2fd3a2b
Not sure u'd get away with it at a rally, especially a large one, as if it falls over then you'd possibly land it on some poor sleeping fella (or child, even worse).
You can always use the BM logo above, I can send a high quality version to anyone who wants it. I suggest getting a smaller pole, say 4m max, and always getting permission from those running the events before putting it up. Maybe 2 with a large banner between would be good (I think it's Alex or Jackie that's having a banner printed already)
Tis me Boss Man banner is being printed as we speak :)
Ken aka Scorpio has made a flag pole which folk saw at Barmouth and will be at Kelso, which is extra sturdy and very unlikely to fall over unless this Fat Lass climbed up it lol