WooCommerce Product Add Ons Ultimate is a WooCommerce product addons plugin – allowing you to configure your products with additional fields and options. It integrates with Bookings for WooCommerce, meaning you can add extra chargeable items to your booking products.
Follow the guidance for WooCommerce Product Add Ons Ultimate to install and create new options in your product. Note that the Bookings plugin adds an extra option for your WooCommerce Product Add Ons Ultimate fields – the ability to charge addon items by booking unit (i.e. per night, per day, or per week) or as a flat rate charge.
See also this article on extra calculation fields that are available through Add-Ons Ultimate and Bookings for WooCommerce.