Lumpia (spring rolls) stuffed with bamboo is delicious and favoured by many locals. Why not try different shapes? For instance, you could whip up bite-sized versions that are small but packed with different flavours. Their tiny size is not only a novelty, but might tempt those who are health-conscious as well.
Bakpia is very popular amongst tourists in the Jogja area. However, you also need to be creative by providing different variations of this pastry. For example, since bakpia is usually baked, you could try steaming. Japanese tourists might find steamed bakpia and interesting choice since its shape is similar to dorayaki, a type of Japanese bean-filled pancake.