Surcharge from product type

Hi All,

I am currently attempting to create a surcharge for samples, my samples are standard products but with a plugin it creates a “Sample” product type when the Request Sample button is used, At the moment I have created a Sample surcharge on the checkout and cart pages when products from a specific category are placed in the cart using the below code:

function woo_add_cart_fee() {

$category_ID = '1718';
$category_ID = '6120';
global $woocommerce;

foreach ($woocommerce->cart->cart_contents as $key => $values ) {
    // Get the terms, i.e. category list using the ID of the product
$terms = get_the_terms( $values['product_id'], 'product_cat' );
    // Because a product can have multiple categories, we need to iterate through the list of the products category for a match
    foreach ($terms as $term) {
        // 23 is the ID of the category for which we want to remove the payment gateway
        if($term->term_id == $category_ID){
         $excost = 5;
         }
         }
        $woocommerce->cart->add_fee('Samples', $excost, $taxable = false, $tax_class = '');
}
}
add_action( 'woocommerce_cart_calculate_fees', 'woo_add_cart_fee' );

These products I have had to create individually and placed in a specific category but would like to remove these and use my sample button as it is so much simpler.

Any assistance would be appreciated.