Try a band of flexible rubber ferrite-loaded shield stuff wrapped around the board?
Could also try a CMC at the tip, but it needs to be good enough characteristic impedance to handle the diff pair properly. Which IIRC you want as short as possible, so, that's a thing.
You might also add some intentional CM impedance, just with a very short transformer/CMC, and resistor, to make a compromise between mode conversion and signal gain.
Tim