If you have a quote  from SO for your total amount due
and wish  to pay with credit card or PayPal account
ask for an invoice with link by e-mail or:

1. Select "Add to Cart" button which will put one cent in your cart.

2.  Increase the quantity to reach the total amount due.
(e.g. For $109.52 add 10952 quantity wit no decimal)

3.  Proceed as normal to complete the transaction.