Search for blacked out bowtie here and you should find a bunch of posts about how to do it. I know you can buy them blacked out and replace the bowtie or add black vinyl to black it out.
Here is a link to a black powder coated front bowtie that replaces they gold one.
http://www.sfxperformance.com/parts/ALS96009K.htm
Ebay is also a good place to look, have lots of bowties and stripes for the new Camaro.
Not sure why you can't get the black stripes on a black car, probably because someone would have done it by accident...your dealer can order and install them but look around locally for a shop to do it, it may be a little less ,expensive. Search here, ebay. or the web and you'll find quite a few options for black stripes.