I have the HD model flag on my Tour Pak (The one you mentioned that looks like it fits on a car window). Mine has lasted a year. It is slightly frayed at the bottom corner but the color has faded from the sunlight. It is easy enough to get a replacement, thought.
The kit from HD has this piece of clear, adheasive plastic that you apply over the paint, to protect it, when you put the flag out for display. For me the plastic wasn't large enough. You can find sheet of this at autoparts stores and cut a larger section. I not only placed the adheasive protector under where the holder clips on, you want to wrap it over the lip of the tour pack/saddle bag, so it covers the inside contact area of the holder as well.
This protects the very edge of the painted portions which are more easily chipped and it keeps the adheasive strip in place. When it gets warm out and you move the flag holder or wash the the bike, or repeated installations of the holder (I cover my bike and to do so, I remove the flag.), the edge of the adheasive strip will start to peel away. Wrapping it over, with excess to the inside of the tour pack prevents this.
Also, I guess you have to be OK with putting a little adhesive on your paint.
Sorry for the ramble. Works for me.
