make disabled dropdown as enabled(only look)

You can do in the following way :-

i) Create the style you want to set for the disabled combobox(similar to enabled text box).
Let say the class name is '.disabledNewStyle'.
ii) Get the disabled combobox in jQuery and add the new class to it.
Let say the disabled combobox ID is 'cmbDisabled'.

Now you can do like below :-

$( "#cmbDisabled:disabled" ).addClass('disabledNewStyle');

// also you can use '.css' method to add styles directly and make it '!important' to override previous styles.

$( "#cmbDisabled:disabled" ).css("color", "black !important");
$( "#cmbDisabled:disabled" ).css("border", "black !important");

Hope this will be of help, at least give you a hint to go in correct way.