You can also buy tire plugs at an auto store. That said I still recommend going to DT or somewhere similar. Incidentally if you buy tires from DT then they patch them for free, and if they can't fix it the replace it.
And to reiterate the tire goo for leaks is an emergency measure, not a fix. It doesn't last, and it makes a mess of the inside of the tire and the rim when it needs to be replaced.