It seems like lots of people are asking about this and I don't see a DIY about it, so here goes nothing. I'm sure this already exists in a better form elsewhere, so please feel free to post the link.
You need some vinyl, a blow dryer, a small sewing needle, and a razor. you can get a roll of vinyl at walmart for like $10.
*disclaimer* I'm not a vinyl guy and this may not be the best way to do it. This is just what I did.
1) Cut the vinyl into roughly the right shape and then stretch it over the bowtie. You can get just about any color, flat or glossy if you do it yourself.
2) Use the blow dryer if necessary to make it lay down. If you stretch it too much at this point it will contract when it cools. The rear bowtie is easier because it is flat and doesn't really need heat.
3) Work any air bubbles out and if necessary, prick them with a needle.
4) Lastly, take the Razor blade and run it along the groove between the gold and the chrome to cut off the excess vinyl.
It sounds more involved than it is. It took me 30 minutes and 3 tries but I figured it out eventually. You can also buy precut decals on eBay. Probably cheaper and easier buy I don't know how the quality is. This is mainly for the DIY guys.