Philip wears this 2 piece outfit in episode 10 of season 3.
The shirt is Brooks Brothers brand and chequed blue. And the pants are grayish/blue with no branded tag.
I believe both items were worn seperately in different scenes, as the the shirt can be seen near the beginning of the episode with Philip talking to Pastor Tim, but on the inside of the pants it is written in pen ' Philip/Scott Disguise' so I believe these were used by Philip when in disguise as Scott Birkeland.