Automatily add a product to cart.

[hotrod]

Allow me to explain..  I run A truck parts store, Some of our parts have a core charge.  A charge you have to pay that gets refunded when you ship your old part back.  For 7 years I could only find the option to have a drop down.. 

1) Return Core First _ No Additional Charge
2) Pay Core Charge Now + 275.00

I can't add it to the price before cart because it then makes the turbo price go up and it looks over priced.  I find many times they miss this drop down and I have to call them and say you selected return core first..  then I have to void the order and they re order..

Once they order I edit their invoice  and add a product (Core) charge and adjust the pricing..

I would love and be willing to pay to have it automatically add the core charge to the cart as a separate product..   

Here is a sample product.
https://hnctruckparts.com/shop-now/drivetrain-replacement-parts-2013-11-18/turbo-s-and-injectors/dodge-ram-turbo-s/1998-5-dodge-5-9l-diesel-engines-w-auto-trans-detail