Plexus for regular maintenance. You can get it online or at most motorcycle shops if they don't carry it at your local auto parts store.
I also use Renovo vinyl window restorer about once every couple of years to get the cloudy look and scratches out.
That's available at
http://carcareonline.com.
[Product ID: 10301 Category: Clear Plastic Care
Renovo Plastic Window Polish - 30 ml Bottle]