Black Widow comprises two parts - standard household paint and metallic auto body paint. No hardware/home improvement store will have the latter. Thankfully, it's very easy to do. Get hardware store to mix part 1, find part 2 online (or local retailer, if you're lucky), mix, apply.
The challenge isn't getting the paint. Surface preparation and paint application require great care as the metallic component of the formula will really highlight any imperfections.
The Valspar Ultra Premium Flat Enamel paint has been renamed by Lowe's to Valspar Ultra Premium Super Flat Finish. The paint is the same so the existing tint formula will still work. You can use Behr 1850 as well and the picture of the Auto Air Aluminum is actually a quart - not the two 4oz...
www.hometheatershack.com
If you go this route, then good luck. The results are worth it when done properly.