I wouldn't use an aresol type paint on your lip. Im assuming its some sort of laquer or enamel which wont hold up as well as quality automotive paint. You should be able to get any Bmw color code paint at all paint suppliers such as Dupont, Sherwin Williams, Basf, PPG etc. You just need to find a supplier near you and you shouldn't have to purchase more than a half pint which would be plenty to do a lip. Of course you will need the clearcoat and activator also. I would not recommend spray silver in single stage. Its really easy to make it look like shit. I have been using Spies Hecker bases on all my Bmw jobs because the match is phoenominal. As is Glasurit. These are pricy paints but they go a long way. I have painted my front bumper, rear bumper, csl spoiler and have enough left over to do side skirts from a pint of Monaco blue by Spies.
2007 335i, 1982 911sc, 1999 Dodge 2500 4x4 Cummins