If you go to Garmin's website, and look at the GPSMAP 62 and GPSMAP 64, and click on the Accessories tab and expand up 'mounts', you will find the bike mounts both take you to the same item:
https://buy.garmin.com/en-GB/GB/shop-by-accesories/mounts/bike-cart-mount/prod11411_010-11023-00.htmlLook at the 'Compatible Devices' tab on that link.
So yes, they are the same.
Be aware that e-bay specials are often poor quality copies, which will drop the GPS unit at the slightest bump.
Get a proper Garmin unit from a proper supplier.
And even then, a lanyard is advisable.
As a rule of thumb, on e-bay, the more often they use the word GENUINE and the bigger the font size, the less likely it is to be genuine.