Perhaps you have already tried this. However, when my daughter was young we bought a bed alarm and it worked really well. A parent of a 12 year old told me about it. It had worked for her 12 year old. I believe we bought it from the Sears catalog, but, I am not sure anymore. At any rate, it was a small alarm that was run by a battery. A sensor was placed under the sheet if I remember correctly. It went off if it got wet.