Once you pinpoint those publications, let them know who you are and what you can contribute to their future needs. Send a query or complete manuscript (whatever they ask for) clearly reflecting your ability to write on that topic area. Also include your background or whatever it is that qualifies you to write such material, plus ideas for additional articles. Indicate your shared interest in and understanding of their particular audience, and volunteer to write articles for them in an emergency.
Most publications are looking for qualified writers they can depend on to meet their ongoing needs.
Even if you don’t get an immediate positive response from an editor, keep submitting to them and work at building that positive relationship. Some editors may be reluctant to trust you until you prove you can write appropriate material, meet their deadlines, understand their needs, etc. Persistence is often the name of the game.