Add cross sell to one off product.

I just purchased your WooCommerce boost sales pro.
I sell unique one off pendants and I simply want the ability for the customer to add a silver chain to the pendant on the checkout page. It appears to me that “bundles” will not work for me since each pendant is a 1 only product. Is there a way I can use your plugin to achieve adding a chain (which I have lots) to a unique “one off” product at checkout?

Thank You for your time.

Antony