The LCP would probably make a good BUG, but probably not in an ankle holster.
I too am thinking about a derringer as a BUG, but in .38 or .357. I saw a nice little IWB derringer holster I liked the other day.
You may have to go with a lighter derringer for ankle holster use. Never tried one so I don't know.
I can buy .38 snake shot at the local gun shop if I want them.
The Bond Arms is one substantial double barrel!! A little expensive, but should last forever! I don't think I want the .410/.45 model due to recoil sensitivity. I can handle .357 ok, but the bigger calibers in a small handgun can be excessive.
Buy what feels right to you and you will do ok.
"We must reject the idea that every time a law's broken, society is guilty rather than the lawbreaker. It is time to restore the American precept that each individual is accountable for his actions." - Ronald Reagan