Create WooCommerce custom stock option that is non-purchasable

I’ve been able to add a new stock option (Call for Availability) in the admin of WP for Woo and it successfully shows on the front-end of the site as well with the following code (using this as my reference, https://stackoverflow.com/questions/43998302/add-a-stock-option-to-woocommerce-3-0).

function add_custom_stock_type() { ?>
<script type="text/javascript">
    jQuery(function(){
        jQuery('._stock_status_field').not('.custom-stock-status').remove();
    });
</script>


<?php   

woocommerce_wp_select( array( 'id' => '_stock_status', 'wrapper_class' => 'hide_if_variable custom-stock-status', 'label' => __( 'Stock status', 'woocommerce' ), 'options' => array(
    'instock' => __( 'In stock', 'woocommerce' ),
    'outofstock' => __( 'Out of stock', 'woocommerce' ),
    'callavailability' => __( 'Call for Availability', 'woocommerce' ), // The new option !!!
), 'desc_tip' => true, 'description' => __( 'Controls whether or not the product is listed as "in stock" or "out of stock" on the frontend.', 'woocommerce' ) ) );

}
add_action('woocommerce_product_options_stock_status', 'add_custom_stock_type');


function save_custom_stock_status( $product_id ) {
update_post_meta( $product_id, '_stock_status', wc_clean( $_POST['_stock_status'] ) );
}

add_action('woocommerce_process_product_meta', 'save_custom_stock_status',99,1);


function woocommerce_get_custom_availability( $data, $product ) {
$stock_status = get_post_meta($product->id , '_stock_status' , true );
switch( $stock_status  ) {
    case 'callavailability':
        $data = array( 'availability' => __( 'Call for Availability', 'woocommerce' ), 'class' => 'call-for-availability' );
    break;
    case 'instock':
        $data = array( 'availability' => __( 'In stock', 'woocommerce' ), 'class' => 'in-stock' );
    break;
    case 'outofstock':
        $data = array( 'availability' => __( 'Out of stock', 'woocommerce' ), 'class' => 'out-of-stock' );
    break;
}
return $data;
}
add_action('woocommerce_get_availability', 'woocommerce_get_custom_availability', 3, 2);

I’m wanting the add to cart button to disappear when this stock option is selected. I’ve tried using this filter:

add_filter( 'woocommerce_is_purchasable', false );

but I’m not sure I’m actually pulling in everything correctly.