How to add a product item without a price amount?

How can I add a product without a price amount in Paypal Payment field. It is a product that needs to be price upon request. 

When setting up a product item, put zero (0) in the price section so it becomes free:

However, if your payment field contains an item with a price value, selecting this altogether with the free item still redirects your submitter to Paypal payment page. Well, only the item with a price is required for payment. 

Alternatively, you can also use our Purchase Order field. No actual payment or redirection should be made. Just to order and up to you to decide the payment method.

Thanks