I'm not aware of any data. In fact, the sex now survey that I quoted is the only data source that I've found that could quantify exposure to conversion therapy, and we think that's an underestimation, because a lot of folks who are exposed to conversion therapy won't turn up in LGBT2QS community surveys, of course.
Absolutely, it should be banned to expose minors to conversion therapy wherever it's taking place, even if it's overseas.