It's rare to find online artwork that's good enough to use as a template for 3d modeling. Usually you have to find a printed source, scan it yourself, and start from there.
One of the largest sources of printed copies of 3-view drawings can be found at
http://www.bobsairdoc.com/
Also remember, it's always best to have two or three samples of the same aircraft. Drawings will seldom match 100 percent. You can never have too much reference material