You need a product called Stormsure. It is a glue which is approved by Aigle and Le Chameau who make rain boots. It is waterproof, clear, flexible when cured and very strong. It sticks to virtually very type of material. Available on the web from many outlets, or on ebay or from the company (also called Stormsure Ltd)
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix shoes.