themeszone

The plugin once activated will display a quantity field with increment / decrement buttons once add to cart button is pressed (e.g. the product is added to cart). 
Thus allowing customers to change the products number in the cart with out having to go to shopping cart 
page.
<a href="http://plugins.themes.zone" rel="nofollow ugc">PLUGIN DEMO</a> 
(click “Add to Cart button to see it in action”)
Feel free to ask any questions at <a href="https://themes.zone" rel="nofollow ugc">Themes Zone</a>

ThemesZone WooCommerce Ajax Quantity

ThemesZone WooCommerce Ajax Quantity Plugin shows quantity field on product listing once customer clicks "Add to Cart" button.

B Hays

Limit the display of product fields with Gravity Forms based on the number of entries.
Currently only works for single product fields with a quantity defined. Limit does not count against entries in the trash.
Great for event registration or product quantity limiting.
Built with Better Inventory with Gravity Forms from Gravity Wiz 
http://gravitywiz.com/better-inventory-with-gravity-forms/

Gravity Forms Quantity Limiter

Limit the display of product fields with Gravity Forms based on the number of entries.

ThemesZone WooCommerce Ajax Quantity vs Gravity Forms Quantity Limiter