If you wanna have fun, there is a company named RealityXP that makes a GNS530 instrument for Flight Simulator that runs the real Garmin firmware.
The only thing I can think of that it doesn't do is simulate satellite lossage, and it may even do that (I haven't encountered it, but I haven't tried). If you pay them extra you get the ability to have more than one unit and cross-fill and such. (It's like $30, $20 extra for the "professional" stuff.)