No any good quality local car parts shop can mix up a tin or spray can for you or worse go to Halfrauds.
Re: Prep - depends what you want to spray I guess the plastic panels? Tricky paint does'nt like flexible plastic - you need to buy a primer for plastics - such as a bumper primer which flexes with the plastic, however generally in my experience durability is still an issue - better off covering in a matching vinyl or leather?
If you do decide to spray then ensure the area is very clean and you may have to rough it up a bit with some very fine wet and dry paper or sandpaper first, apply primer , dry then apply another coat etc then paint, dry , sand , repeat until you get the finish you want?
Hope this helps?