How to add a fix charge to a PO stock line on order entry with advance pricing?

Hello,

As the title says, how can I add a fix fee for a PO line for a stock item.

Scenario:

Supplier charges a fix cost price of 10 USD regardless of the quantity ordered on the PO for Item A.

If Item A = 15 USD and I order 5 EA, then it should be

5 * 15 = Extended cost of 75 USD + 10 USD = 85 USD

This charge need to affect costing of the item (02). So adding a non stock line for example is not an option. Also the cost needs to be reflected during PO Entry.

Same orders can contain other line with Item B which has a different fix charge.