Best thing is to get a popular name in social media. Start a Facebook page, even. Once you get the ball rolling, and a decent number of followers on the facebook, it's cheap to 'promote' posts to ensure they show up in peoples feeds. I work with a nonprofit who spends ~$20 to "promote" the events on Facebook and our attendance is typically 4-5x what it is without promoting.
Instagram, Facebook, whatever... get your name/product on social media. Make a website. Make it nothing more than a simple landing page with a couple GOOD photos and contact information. Doesn't have to be anything else. One page. 3-4 files total. Exploit that until you're ready to set up your own website with retail capabilities. That'll be around the time people want to stock your parts in their shops, too.
Good luck. That's a pretty tough hill to climb these days - AR parts. You better have something worth promoting, and as stupid as it is, a good photographer that will get people spreading pics. Doesn't have to be anything that "properly displays the product features" but simply a pretty picture. Look at Stickman, who's typically under a name like 'stickgunner' on FB and IG. Guy does a looooot of firearms photography and sometimes it's not at all commercial product imagery. It's sometimes just neat pics that make their rounds on the internet a lot. Gets your name around.