This model provides a cap for a 1/4-20 monopod and a clip for its shaft in order to hold a flag.

No supports should be needed and it should be able to print with your default settings. Use a 20mm M4 bolt through the rivet of your flag to hold it to the cap and clip.

I got my monopod at a garage sale, but I'm pretty sure that this monopod is the exact same one as mine, just with a different brand sticker on it.