Anything other than stainless steel will rust. If you want black get something like this:

http://www.amazon.com/BPARTS-Stainless-License-Screws-Fasteners/dp/B00B5ZYY38

or this:

Anti Theft License Plate Security Screws Stainless Black Mirror Snap Caps | eBay

 

...these are great ! (rear)...no rust durable nylon bolts, w/nylon bolt-covers...bout 3 bucks:

#81

 

I would go to your local hardware or marine store and pick up 4 stainless steel screws (that match the thread, width, and length of the screws from the dealer) as well as finish washers for each.

Plasti dip or paint the screw heads and washers black if you want.

I replaced mine right away since the ones from the dealer rusted within a month here in FL. A quick trip to Waste Marine did the trick for less than 3$.

 

I know Home Depot has those bulk sections where you can buy 1 screw at a time.
I can't say I've ever had a problem with rusting screws, but now that somebody mentioned plastidip...!

 

I'd like to mount my new plates on the front without drilling,anybody have any photos and a link to what worked for you?

 

You can get 3M automotive double sided tape, that stuff is strong!