It depends on which state you are in. It is easier to find 80 proof vodka in general. Just ask at the liquor store.
Probably the most important thing to do when using dried cayenne is make sure the heat units are high. Pacific Botanicals 150,000+ HU habernero peppers are very hot. I suspect they use 150,000+ to designate the low end of the range. Don't use 40,000 HU stuff that is more commonly available. Go to Pacific Botanicals, Blessed Herbs, Botanicals, or Mountain Rose Herbs. They all have good stuff. I'm sure there are other good suppliers, those are just the ones of which I am aware that have primo stuff.