the FrSky Taranis x9d does have one option available to it that i have been using for the last two years. it works well, but not as good as a 40mhz setup would work.
FrSky makes a transmitter module that plugs into the back of the x9d, as well as several different receivers...
these are made for long range drone flying, but, as i have said, i have been using them exclusively for my model submarines for the last two years (everything else r/c uses 2.4ghz)
these use 915mhz for USA, and 868mhz for europe.
I personally own two of the r9m modules, and the following receivers:
2 original r9 receivers
2 original r9 slim
3 original r9 mini
although most of these receivers have been replaced with newer models, I don't think there is a direct replacement for the basic r9 receiver, which is kind of a shame.