You might have better luck in Port Isabel. There used to be a souvenir shop on the south side of 100 before the causeway that had interesting stuff. Also, the lighthouse museum might be of interest. SPI is mostly gaudy t-shirt shops filled with cheap trinkets not worth the price. Unless that's what you're looking for.. I'd also recommend stopping at both the PI and SPI Chambers of Commerce. Someone there should be able to point you in the right direction.