I\'m using UITextField as a UISearchBar replacement and \"stealing\" the magnifying glass icon from the original UISearchBar with this
So, here's the code with the unicode character:
UILabel *magnifyingGlass = [[UILabel alloc] init];
[magnifyingGlass setText:[[NSString alloc] initWithUTF8String:"\xF0\x9F\x94\x8D"]];
[magnifyingGlass sizeToFit];
[textField setLeftView:magnifyingGlass];
[textField setLeftViewMode:UITextFieldViewModeAlways];
Edit: For plain look that fits iOS 7 style, add Unicode variation selector \U000025B6.