A great flagpole are those polls used by pool cleaning people. I've found three of them on the side of the road over the years. (You ever see one in any manner secured in a pickup truck?) The poles look weak in their extended position, but, no, they are high quality aluminum and not weak at all.
Secure it to the tallest upright you have in your structure and the flag will be high enough to see from blocks away.
If you don't feel the need for an exotic flag, just get some cheap rip-stop nylon at a fabric store and make something identifiable to your friends. In the flag below, the seams are glued.
My ripstop flag has been attached to the pool pole with Duct tape for years. The pole has never bent.
As was said, send a pic of the flag to all your group.
And, as a bonus, your neighbors will love you for your flag.
I've had blinkies last almost the whole week, on 24hours/day.