An accessory system for a vehicle includes an attachment element bonded to an in-cabin windshield surface at a first windshield location and an attachment member attached at the in-cabin windshield surface at a second windshield location. An interior rearview mirror assembly has a mirror support that has a mirror mount configured to mount the mirror assembly to the attachment element. A module is configured to be received by and be supported by the attachment member attached at the windshield. With the module received by and supported by the attachment member at the windshield, a camera of the module views through the windshield and is part of a driver assistance system of the vehicle. With the module received by and supported by the attachment member at the windshield, the mirror mount can be mounted to and demounted from the attachment element without demounting the module from the attachment member.