WooCommerce: add extra images to product gallery

I want to add some extra images to the product gallery. Based on a meta field from a different post. The images should only add to the gallery in the frontend. Not to the image gallery of the product itself.

EDIT: @mujuonly was right. I could use woocommerce_product_thumbnails and so I tried the following code and everything works fine:

<?php 
add_action( 'woocommerce_product_thumbnails', 'custom_product_add_thumbnails', 100, 0 );
function custom_product_add_thumbnails(){
    
        $extra_gallery          = get_field( 'some_field' );
    
        if( $extra_gallery ): ?>
    
            <?php foreach ( $extra_gallery as $image_id ): ?>
                
                <div class="woocommerce-product-gallery__image">
                    <?php echo wp_get_attachment_image( $image_id, 'woocommerce_single', false, array( "class" => "" ) ); ?>
                </div>
            <?php endforeach; ?>
                
        <?php endif;
        
    endif; 
               
}

With 100 in the action the images are shown at the end of the gallery:

add_action( 'woocommerce_product_thumbnails', 'custom_product_add_thumbnails', 100, 0 );

Answer

add_action( 'woocommerce_product_thumbnails', 'custom_product_add_thumbnails', 100, 0 );
function custom_product_add_thumbnails(){
    
       // Echo images here
               
}