yeah, head to the grocery store and either get fresh seafood mix /shrimp with shells, mussels, squid, or get a frozen mix, just make sure it has nothing added.
.......also, be sure the puffer gets something to keep his teeth trimmed. Shrimp shells help; if you toss an opened raw clam in the tank all your fish will go nuts and the puffer often will chew the shell. I wedge a piece of cuttlebone (for birds, non-medicated) in the LR and my puffers have always used this.