how to make redirect product to shopping cart

[sivanmen]

hi there to all,

i have a site , joomla 3.4 + virtuemart 3.
in the backend i make 3 service prodact with price and data.
the change i wont to make is in the display in the front side. i don't wont to publish it as a virtuemart prodact.
i would like to make in a contact page a button, pay now!, which will lead to shopping cat and will add the virtuemart prodact .

how can i make redirect to shopping cart and it will add the virtual prodact?
what is the URL redirect that i need to put in the bottom?
demo:
http://idodo.dealyad2.co.il/%D7%92%D7%B3%D7%95%D7%9E%D7%9C%D7%94/%D7%A1%D7%A4%D7%95%D7%A8%D7%98-%D7%95%D7%9B%D7%A9%D7%A8-%D7%92%D7%B3%D7%95%D7%9E%D7%9C%D7%94/118-hawkstore