Can anybody recommend a waterproof lunch bag for my son. In his lunch bag I put his water bottle and lunchbox. He always forgets to put the lid down on his bottle and it leaks through his lunch bag and into his school bag. His pencil case and some art he took home were soaked today. I do not want a bag with an outside bottle holder because I know he would lose the bottle. He is very forgetful. I remind him every day to close the lid on his bottle. Any recommendations would be great because his current lunch bag (wildkin brand) is not waterproof.