I would check some of the thrift stores for corduroy and denim or even estate sales. Heavy flannel or cotton blankets would work well for batting. They've probably already been washed so no worry about shrinkage and washable. Did he say what size he wanted. One way of checking the weight is to gather all your material together, put it into a basket and weigh it. By the time you add the tying and binding, I'm sure it will be very heavy. Good luck and please share photos.