Replacing the <ion-select> button texts by icons


I am looking for a way to replace the placeholder texts in an ion-select action sheet with icons instead of simple text.

Now, I know the texts can be changed by adding ‘okText’ and ‘cancelText’ to the HTML:

<ion-select multiple="true" [(ngModel)]="selectedGenres" (ionChange)="filterByGenre()" okText="Okido!" cancelText="Nah, whatever..">
            <ion-option *ngFor="let genre of genreList" value="{{genre}}">{{genre}}</ion-option>

But what would be the best ways to add icons to those buttons?

For instance, I would like to replace the OK text with e.g. ‘ion-android-checkbox-blank’ icon and CANCEL text with e.g. ‘ion-android-close’ icon.
Reference: Ionic Icons Cheatsheet