Hi,

There are just two Models available for the Flightsimulator at the moment. The first one is from Jorge Sanchez and the second one from the Historic Jetliners Group (HJG). HJG didn't have their J31 on their website any longer but you could still find some models when searching for HJG and J31. The same for Jorge's model. Just search for Jorge Sanchez on Avsim or Flightsim.com. I think you should find some models from him.

Unfortunately I've never checked if those aircraft work in FSX so I could not say anything about this.

Best Regards
Matthias