Sumatra beans seem hard to find recently in Starbucks, Mandheling French at Kaldi is a good replacement.

Mandheling is a type of Sumatra and has the same low level of acidity as Starbucks Sumatra. (They are probably from similar beans.)

Mild taste, easy on your stomach. After going to three Starbucks and not finding them, I got my fix from Kaldi.