Adding extra custom user fields to the WooCommerce checkout

I’m looking for a way to add extra custom user fields to the WooCommerce checkout for when a first time buyer checks out and registers at the same time. Ideally this would be a plugin rather than PHP coding via hooks. These fields could typically be for a secondary contact phone number, email, etc. I just want to be sure that when the customer checks out (and registers to become a full WordPress user) that these fields are saved as user_meta fields, and they don’t just become order_meta fields or part of the WooCommerce ‘customer’ object – i.e. they need to be linked to the core WordPress user object and appear on the user profile page in WordPress admin (similar to how billing and shipping fields appear, but preferably in a separate section). I know how to add extra fields to the registration form (either standard WordPress or WooCommerce), but this would need to be part of the checkout form.

Many thanks!