NavBarSetup.swift

- (void)setupNavBar {
    self.dismissButton = [UIButton buttonWithType:UIButtonTypeSystem];
    UIImage *dismissButtonImage = [UIImage imageNamed:@"close-large"];
    [self.dismissButton setImage:dismissButtonImage forState:UIControlStateNormal];
    self.dismissButton.tintColor = [UIColor cookingBlack];
    [self.dismissButton mas_remakeConstraints:^(MASConstraintMaker *make) {
        make.height.equalTo(@44);
        make.width.equalTo(@44);
    }];
    [self.dismissButton addTarget:self action:@selector(dismissButtonTapped:) forControlEvents:UIControlEventTouchUpInside];
    self.dismissButton.accessibilityIdentifier = @"Close";
    UIBarButtonItem *dismissBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:self.dismissButton];
    [self.navigationItem setLeftBarButtonItem:dismissBarButtonItem];
    self.navigationItem.titleView = self.loginTopMessage;
}

This probably is a really bad idea, but perhaps it could be finessed into what your designer is looking for...
https://gist.github.com/scottswezey/f491a39421f14ac6eeaa5654a148cc32