I currently make flags specifically for Venture Rider .Org members. I make the 6x9 antenna flag as well as the larger 9x13 flag. Both can be pole mounted.
I recommend nothing larger than the 4x6 for antenna mounting. The 4x6 flags will also last much longer than the larger flags.
I recomend http://www.m-j-enterprises.com/ They have a large variety of mounts and fair prices.
I make all varieties of flags and custom order flags are welcome. Custom windshield covers are also available.
You can see some of my products here: http://http://www.timenagainphotos.com/mp_includes/pages.asp?id=1425 Scroll down to see the individual flags. Members of Venture rider also get a nice discount from the prices listed.
These flags are double sided, Polyester fabric, double stitched, the image is Dyed into the material, it cannot peal, chip or flake off. they are made to hold up at highway speeds. Check, money orders or paypal are all accepted.