In Tanah Rata town, there are travel agency who can organize a jungle trekking for you to explore the nature of Cameron Highlands, there are giant Raffresia, water falls and native people villages hidden in the natural rain forest. If you spare extra one or two days in Cameron Highglands, you can arrange for another amazing experience.
From the poster I saw at their offices, the travel agency can help you to organize many continuous journey in Malaysia, including to Taman Negara.