Two words say it all: SHOE GOO. I snipped the following description from a retailer online: “Shoe Goo is a clear adhesive and sealant that easily and permanently repairs all types of footwear. Apply it directly from the tube to worn out areas, allowing it to harden overnight. Shoo Goo adheres to all kinds of materials, so use it to mend rubber soles, tears in canvas or leather tops or to stop shoelaces from fraying. It dries to a waterproof, flexible rubber, so it will repair waders and boots without breaking or cracking under stress. Commonly used to cover pitching toes on baseball or softball cleats, mend worn outsole areas especially on running & skateboarding shoes, and repairing loosening outsoles.” See: http://www.weplay.com/Shoe/Goo/ Expect to pay around $6 per tube. Wal-Mart sells it, as well.
Shoe Goo is not as durable as the original sole on running shoes, but you can easily double the life of your footwear. And it is easier to pack a tube of Shoo Goo than extra boots. – OSOM