Well "the pet shop" here in Maui did not have any freshwater shrimp but the owner did say that I could probably just get a fine mesh net and catch my own and she would bag them for me and package them. Then I could have put the box into a checked bag since I think you can have more than 3 ounces in a checked bag but I am not sure. You will have to catch your own shrimp in the mountain rivers unless you find a pet store that sells them though.
I am currently trying to get home on standby at the airport, which is a nightmare, but another problem with taking the shrimp is they dont allow you to take flowers, fruits, and other "agricultural" stuff so I am not sure what they would do about shrimp
I was unsuccessful, but good luck to anyone attempting to get a few mountain shrimp. For me it was more of if the opportunity arose I would bring them back but you will alctually have to visit the mountains with the streams the shrimp live in, which I am sure would be a pleasant hike if you are with family like I was.