There's a Southwest 737-700 with winglets by Erick Cantu in the "New Mexico" scheme which is just stunning:
This is all found at avsim.com
They also have the Kittyhawk 737-700 (which I believe is by Erick Cantu) on avsim in the Maryland One scheme, classic scheme, Nolan Ryan Express scheme, and....the New Blue scheme!
Look in the avsim.com file library under FS2004 for "n202wn.zip" It also appears that he revised it so look for this file as well "dgoupdt.zip" Both are for the Kittyhawk 737-700 which is easily the best out there.
Here's the file info for each file:
This is a Repaint of the Project Kittyhawk 737-700 as Southwest Airlines N202WN. Features the aircraft in the "Canyon Blue" paint scheme with "SOUTHWEST.COM" on the outboard surfaces of its blended winglets. A complete ready to fly aircraft for FS2004. Original aircraft by project Kittyhawk. Repaint by Sam Kimpton.
This file contains an additional texture set and revised aircraft.cfg file enabling one to upgrade my previous upload dgov1.zip (Southwest Airlines 737-7H4 The Donald G Ogden) to include blended winglets with "SOUTHWEST.COM" on their outboard surfaces. This upgrade reflects the current appearance of the aircraft. REQUIRES dgov1.zip by Sam Kimpton original aircraft by Project Kittyhawk. Repaint by Sam Kimpton.