There are many configurations that can be used to convert from differential to single ended. The most straight forward configuration is to use differential pair amplifier with single ended output. If the amplifier output impedance is high as the output will be taken from the drain of one of branches of the differential amplifier, one can cascade it with a source follower.In this way you can match well a low load resistance.
So, the required circuit can be built from from single ended differential amplifier followed by source follower.