1.) Request it or paint your own.
Maybe you have more luck at http://www.sim-outhouse.com/index.php?page=main&loc=pages
Just note that they are currently down for maintaneance, should be back up in a day or two.

2:) To use a downloaded plane in campaigns mode you'd have to add it to the campaign's techtree.
The campaign's file is located in "yourCFS3root\campaigns\fortress europa.xml"
You can open and edit the file with a tect editor or a special xml editor.