If you’re looking for books you can get them at Amazon, Barnes & Noble, and other fine retailers.
The Summer Job T-shirt was designed by Trevor Henderson and are available here.
Exponential , Zero Lives Remaining, Video Night shirts are available via Amazon Merch. These were designed by the incomparable Chris Enterline.
T-shirts from Skurvy Ink Press are temporarily unavailable but they were offered in The Summer Job (art by Justin Coons), Tribesmen (also by Justin Coons), and Video Night (art by Nick Gucker) varieties.