I just ordered one of the "If you haven't served" decals... can't wait to get it. Got it from http://stores.ebay.com/thinbluelinedecals I think these guys are the official ones.
I've ordered several thin blue line decals throughout the years and the only ones that lasted were the ones from here http://www.fireandrescuedecals.com
Comments
http://www.fireandrescuedecals.com/the-thin-blue-line-decal-sticker-black-blue-reflective-118
I bought this decal from the same place and it's the best one I've found so far.
http://www.fireandrescuedecals.com/thin-blue-line-wouldnt-understand-decal-sticker-149
http://www.fireandrescuedecals.com/some-gave-all-thin-blue-line-sticker-decal-158
2015
I just picked a couple of these up and I have to say these are by FAR the best TBL stickers I have come across. Here's a link. http://www.fireandrescuedecals.com/carbon-fiber-thin-blue-line-decal-sticker-reflective-stripe-163