There's no shoe polish that I know of that can withstand water for a reasonable period of time while maintaining the nice shine on the shoe. The porous nature of the leather on the boots makes it difficult to make a polish that shines while withstanding the effects of the weather.
Judging by the amount of products that are available, I'm certain there has to be such a polish, but I doubt it will shine well and it.
Here's an alternative that will withstand the rain/snow, but it's not a polish, rather, it's more like paint.
Leather Luster