Our flagpole is a 28-foot fiberglass telescoping pole. We bought it for around $60 from a vendor in Quartzsite, AZ. A similar pole can be found on Amazon. It uses friction to keep it up and moves up and down very easily. It has scratched a little since it collapses inside itself.
Tim made a holder that mounts to the front of the Airstream from a few misc. pieces purchased at Lowes. A section of 2-inch black PVC pipe (Lowes had precut 2-foot pieces for a few bucks), and two pipe reducers finish off the top and bottom while holding the flagpole tight.
The PVC pipe section is attached to the Airstream’s jack tower using four 2-inch conduit hangers. They worked great except for the little extra bump and hole. After these photos were taken they received some black paint to better blend with the PVC. When collapsed, the pole is both short and secure enough that we are able to leave it in the holder when we travel.