For a minute I was think frSky, I have not seen one for flysky as of yet and I have been on the 9x now for almost 2 years. This does not mean one does not exist, I just have not seen one yet.
I would have to agree with lee on the frSky stuff. If you want a solid link go with the frSky duel antenna RX. Distance is estimated ant 1.5Km, mileage may very (pun not intended ).
Even if you go with 3GX then satellites are still an option and in most cases the better option. Depending on your TX though you may not have that option and if that is the case then a standard RX will be needed. Now if you have a TH9X(R) the the frSky module would be a great option.