https://www.amazon.com/Herb-Pharm-Extract-Musculoskeletal-Support/dp/B0016B7TC4/ref=sr_1_3_a_it?ie=UTF8&qid=1490711236&sr=8-3&keywords=cramp%2Bbark&th=1

I haven't personally used it yet, but the reviews convinced me to give it a try.