Prestashop plugin : Custom field on product page

Hi, i want a simple prestashop add-on that do the following :

- Adds an input type number on product page as custom field
- Display custom product field on back-office (order, invoice)
- When adding the product to cart, multiply the product price by the number on the field

(Example : product cost 20, if the input number is 3 --> when added to cart the price will be 20*3 = 60)

I want this as a standalone plugin
Low to medium budget.
Thank you !