Unfortunately, I've had no luck locating a local source for limu kohu. The stuff apparently doesn't freeze too well and goes bad quickly. I once tried to have some expressed to me from Honolulu...that didn't work out so well. If you're not a poke connoisseur, Japanese seaweed or the freeze-dried stuff in the Noh brand poke mix may make for a passable product.
I have found that andouille and linguisa work fairly well as substitutes for the stuff we call "portuguese sausage" back home. I usually end up using the Aidell's brand andouille (when on sale) for Portuguese Bean Soup. My Hawaii-raised housemates are fine with it. Sorry, I can't help you with blood sausage--it's not my thing.
As far as other Hawaii-based goods, what are you having trouble finding? With the exception of poi and some local condiments (like chopped kukui nuts), many ingredients that you'd find in Hawaii are available in Chicago's Asian markets.