It is my understanding that AFTER a sale has been made it is OK to swap email information. (At least it used to be - I am not sure of that has changed - anyone?)
IF that is the case then ask them to send you their email address so you can generate an invoice through Paypal for the additional.
BUT it may all be a fool's errand. By the time the invoice is sent and paid and then because the post office has cutoff times you may not meet (making it in effect 2nd day air not express)_ they may find themselves paying a whole lot of extra money just to get it the same time they would have if it went regular Priority Mail.
On those occasions when I have been asked for an upgrade and I told them, sure - an additional $40.00 to speed it up by one day they say "never mind".
"Laissez-faire capitalism (AKA The Great Material Continuum) is the only social system based on the recognition of individual rights and, therefore, the only system that bans force from social relationships." ~ Ayn Rand
