These are rare as hens teeth even in the UK, you are most likely going to have to wait till someone breaks a pair of M3's.

Given that it is a ported design with the active crossover tailoring the response of the B110 above 1Khz I cannot imagine any other driver working well.

Rgds
Stuart

Linn LP12, Ittok LV11, Arkiv, Linn Kairn as a phono stage, MPmax 221, DSP6000's, WiiM Pro streamer.