marker.setZIndex(999);

google.maps.event.addListener(marker, 'click', function() {
  console.log('Marker clicked');
});

var marker = new google.maps.Marker({
  position: location,
  map: map,
  icon: {
    url: 'path/to/icon.svg',
    scaledSize: new google.maps.Size(40, 40),
    anchor: new google.maps.Point(20, 20)
  }
});

.custom-marker {
  pointer-events: auto;
}

function CustomMarker(latlng, map) {
  this.latlng_ = latlng;
  this.element_ = document.createElement('div');
  this.element_.className = 'custom-marker';
  this.element_.style.position = 'absolute';
  this.element_.style.cursor = 'pointer';
  this.setMap(map);
}

CustomMarker.prototype = new google.maps.OverlayView();

CustomMarker.prototype.onAdd = function() {
  this.getPanes().overlayMouseTarget.appendChild(this.element_);
  google.maps.event.addDomListener(this.element_, 'click', function() {
    google.maps.event.trigger(this, 'click');
  }.bind(this));
};

// 使用
var marker = new CustomMarker(latlng, map);
google.maps.event.addListener(marker, 'click', function() {
  console.log('Custom marker clicked');
});