I have a spring loaded flag holder like this that clips to the bumper. I would recommend a better flag tho. I self distructs at speed!!
http://brattons.com/product.asp?P_I...artPosition=1&strSearchCriteria=any&PT_ID=all
Here is the American flag I use. It is hemmed all around so it doesn't fray like the 'cheapies'.
http://www.ebay.com/itm/150635956119