Is there any way to synchronize multiple AD9262's for phase coherent operation across multiple parts?
Unfortunately not since it was not considered during the product defintion phase.
You may want to consider the AD9650 (83 dB SNR at 105 MSPS) which provides similar dynamic range in DC to 10 MHz region as AD9262. Since this is a standard ADC, one would need to perform decimation in the digital host if oversampling is preferred. The AD9265 may also be a good choice if you can live with 79.5 dB SNR at 105 MSPS. Both devices feature SYNC capability. Regards.