I had to google that! and found the phrase "I’ve got a fever and the only prescription is more cowbell" from Christopher Walken.
The Indonesian for that would be "dan satu-satunya resep/obat adalah lebih banyak lonceng sapi". If you want to use the word "hanya", you can say, "dan resepnya/obatnya hanyalah lebih banyak lonceng sapi."
resep = perscription obat = cure/medicine