I get mine at: avsim.com simufly.com simviataion.com flyawaysimulation.com
The vast majority at avsim. Some files are exclusive to other sites so I have to move outside of my comfort zone.
Those are my daily stops.
Then I surf the forums for something that has been found elsewhere in the worlds pages.
Click the links on every site I go to, you can make some amazing finds.
Shop's (Last resort)