Rock Bass range maps indicate they are found in most of eastern Iowa. Just go to a bait store and ask, you'll probably get directions to a spot where you can catch your own. They are aggressive biters and usually easy to catch. Use barbless hooks, or just pinch down the barbs on a standard hook with pliers, to make removal from the hook easy without causing damage to the fish. Handle the fish with wet hands to preserve the slime coating. Don't wait for the fish to swallow the bait deeply; you want to set the hook when it's just held by the lips. Injuries like this heal quickly and completely; I've caught many aquarium specimens this way without issues.