I think I'm reading right that he has an existing 2G switch that controls two lights, and he wants another 2G switch to control the same two lights.
Options are therefore:
1 - replace the existing 2G switch with a QU RS2W (and yes as above a 25mm box is needed).
OR
2 - Fit receivers at both lights (e.g. QU R303) , and dispense with the existing conventional 2G switch.
In both cases the new switch can be any transmitting switch, e.g 2 QU WS2W, or made up of grid switch modules. Just not a receiving switch.
You could also add a key fob switch, or PIR, to turn a light on before you get there.
For a long time there were just receivers and transmitters, and things were simple! Then they added the receiver-switch range for this exact scenario.