I Was Diagnosed With Kidney Stones Last Week. The Doctor

I was diagnosed with kidney stones last week. The doctor has prescribed naproxen and buscopan. However I am going to the Caribbean this week and am extremely worried in case I get the excruciating pain I got a few weeks ago before I was diagnosed. I am worried in case this pain happens on the plane. The doctor will not prescribe anything stronger such as morphine for me to just have for the trip. Is there a strong painkiller you could recommend which I could get over the counter please. It would make me feel a lot easier about travelling.