I am working on a site that uses the Commerce module for a web store. The design specifies that the user's cart overview page should allow them to increase and decrease the quantity of a particular item using plus/minus buttons. However, as far as I can see the only option for a quantity field is a bare text field (in commerce/config/line-items/product/fields). I've searched for solutions online, but apart from the Commerce Extra module (which is in alpha, and does not allow for vertically-stacked buttons as per the design) I'm coming up blank.
Is there an 'accepted' way to add these buttons to the quantity field, or am I missing something in my configuration?