http://www.dogchatforum.com/belly_bands_dog.htm
Excellent link and easy to make. I used 4" flannel, double fold, velcro on opposite ends. Measure around the belly, allow for lap over, Incontinence pads (Ultra) while I am at work. Successful solution for Charlie and will have him wear one when I am on our vacation at my daughter's house. Don't want him to mark because this will be new territory.
PS Since he marked his territory when he came to live with me, I do not allow another male dog inside unless they are wearing a belly band.