I need to make another invoice as my estimation for international shipping was short, solution?

[dhbookds]

You can't change the amount for $ shipping after the item has been sold, if that's what you mean.  The buyer bought based on what your listing stated. 

[varebelrose]

If the buyer has already paid based on what was set up for shipping in the ad, you cannot ask for more money. We have all made the same mistake at least once, but its on you not the buyer.  Lesson learned the hard way.