Here is a working example of above. http://jsfiddle.net/z7L6m2sc/ Now select2 has been updated the classes have change may be why you cannot get it to work. Here is the css....
.select2-dropdown.select2-dropdown--below{
width: 148px !important;
}
.select2-container--default .select2-selection--single{
padding:6px;
height: 37px;
width: 148px;
font-size: 1.2em;
position: relative;
}
.select2-container--default .select2-selection--single .select2-selection__arrow {
background-image: -khtml-gradient(linear, left top, left bottom, from(#424242), to(#030303));
background-image: -moz-linear-gradient(top, #424242, #030303);
background-image: -ms-linear-gradient(top, #424242, #030303);
background-image: -webkit-gradient(linear, left top, left bottom, color-stop(0%, #424242), color-stop(100%, #030303));
background-image: -webkit-linear-gradient(top, #424242, #030303);
background-image: -o-linear-gradient(top, #424242, #030303);
background-image: linear-gradient(#424242, #030303);
width: 40px;
color: #fff;
font-size: 1.3em;
padding: 4px 12px;
height: 27px;
position: absolute;
top: 0px;
right: 0px;
width: 20px;
}