The only coils available for Equinox that will work are the 6", the stock 11" and the 15" all are butterfly DD coils from Minelab.
There are no after market coils that work for the Equinox at this time, not compatible with coils from other detectors and it is not just a connector pin issue, there is a micro chip in all Minelab coils that talks to the control box, different chip for each detector. Coils for Minelab Explorer series, Safari and ETrac are all compatible with each other but not with Equinox.