For some niches you will find that there is an abundance of free press releases available. This is particularly true of the technology industry, but many other market places also generate significant volumes of news.
Sometimes you will find press releases on the individual company sites, other times there will be an industry body the distributes news releases to all appropriate parties and usually they will make them freely available on their web site.
Usually news releases come in a format that allow you to edit them. This can be particularly useful if you want to include some of your chosen keywords and phrases. Obviously, it is not ethical to change the meaning of the press release by adding inappropriate words and phrases, but it is fine if the words and phrases you add do not change the press release to the point where it is no longer accurate.