You might also look into various sparkly nail polishes. Nail color is also enamel and can be blended/ mixed into Testors hobby paints without any problems. Beyond that, its pearlescence has a wide degree of granularity, from very coarse (like glitter) to extremely fine & metallic, which makes it a good add-in for matching the pearl of an original paint.

Speaking as a pro illustrator with over 30 years of experience, I'd never use a tube-based acrylic for something like this. Even though it's still grossly unsuitable, a 'jar' acrylic will give you better results.
See, acrylic paint in its 'raw' form is liquid, just like latex house paint; in order for it to work out of tube (like toothpaste or traditional oil paint), minute polymer strands are added to the paint, making it viscous. All fine & dandy; however, the downside is that once this is done, you'll never be able to thin it out evenly again; you'll always have streaking because that extra polymer will tend to bind to itself on your surface just as it does inside the tube.

This isn't to suggest that I'm opposed to acrylics on a bike. I often use 3-part automotive paints when I fully repaint a frame, and I'll usually have it mixed & matched at a custom car shop (the accuracy of the color is worth the cost). This starts out as a pretty normal liquid acrylic latex, but you then add a solvent & a hardener in a precise mixture. You have to be careful with this for a variety of reasons- and the clean-up has to be quick & thorough (lest it dry inside- and thereby ruin- your airbrush)- but the final surface is quite hard and can be sanded & polished.