Pass a non-bound input value to arraycontroller via an action in ember

I'm rendering a iterative template that contains an input field and an action to my array controller, I can happily pass the current model but I'm a loss as to how to pass the unbound input value contents.

To give a totally simple example, think of a list of products template on an ecomms site, with a qty field and update button.

{{#each product in controller}}
   {{product.name}}
   <input name="qty" placeholder="Qty" />
   <button {{action addToCart product}} ></button>  
{{/each}}

This is a simple product list, not a view cart contents list so the qty field has no business being a part of the product model. I need qty to remain unbound (always loading blank)

How can I pass the value of the qty field to the addToCart action?