D.W.
I use cloth, so I haven't actually tried this suggestion but my mother in law swears by it. She says, double diaper them at night. First diaper has a slit or hole cut into it to let some of the fluid leak into diaper number 2 which is obviously intact. I'm not sure if this would actually work or if the little gel absorbers would leak out of the diaper that is cut. This is advice from when she had kids, more than 25 years ago.
Another thought is, you could get a couple of cloth diapers and use insert doublers. That is what we do and we don't have any leaks ever. I love our cloth diapers (bum genius 2.0). Our daughter is only 1 but she doesn't leak and is a big drinker. We even still give her drinks throughout the night if she wakes up, since she has stopped nursing. If you want to check out this option go to www.wildflowerdiapers.com they are based out of scottsdale so you can actually go to talk to the owner if you need to. Good Luck!