RedTube is a big porn video site that features both gay and straight content. Although it doesn't have a dedicated category for ebony studs getting dirty on camera, what you can do is search for 'gay black' and find material that is relevant to that niche. Note that the link I've provided here will take you immediately to that section: no need to thank me!
The search results for these keywords is a little on the small side with just 1,300 scenes to look at. Sadly, a number of the clips appear here under that keyword that don't feature black dudes at all. The good news is that the thumbnails allow you to figure out what content is and isn't relevant to what you're after, so there's no need to panic: you will have all the gay black porn you want, it just requires a little bit of detective work in order to get there.