Here is an idea:
Buy them a prayer.You pray, ask God what to buy, and wait 24 hours for God to sift some ideas through your mind, praying for him/her while you wait.
In that purchase, even before a great present is made known to you, you gave two very important gifts:
For the one who has everything, you gave God an invitation to focus on him or her.
And, for the One Who has everything, you gave a focus on Him for His birthday.Awesome shopping.