No problem getting a script from my doc for Ambien for jet lag. However, I did have one problem on my last trip: I left my little vial of Ambien on the plane and couldn't get a replacement for the rest of the trip. In China and HK, it didn't exist; in Manila it did but needed a prescription from a local doctor (not worth bothering getting); and I didn't even TRY in Tokyo!
In China they sold me something called "Zopiclone" cheaply (Lunesta is "eszopiclone"), but when I looked it up online, the side effects listing scared me away from trying it.