Petsmart and most fresh water fish stores will carry elodea and duckweed. The Water lettuce and Hyacinth i find at a pond store. i just one of any of these and just toss it in the tank and just leave it in there. one water lettuce probably last my 4 baby Yellow bellied sliders 2 days. its really low maintenance with the aquatic plants because you can leave them in there until the turtles have completely eaten them. unlike with lettuce and other greens if they arent eaten after a while they must be removed or they will spoil the water. anyways just call around to some petstores and pond stores and see if they have that stuff. let me know if you have any luck