Darren, If you can find the SEM product in the right color, that sounds like the easiest way to do it, but if not here's another suggestion. If you can find the original PPG formula number for the interior color, you can have it mixed in laquer, then add a flex agent PPG sells. You'd have to spray it yourself with a detail gun, but I've done this many times on plastic and vinyl interior parts and they turned out great.
Verne