Salt tablets, or electrolytes? If just salt, there is usually plenty available at bars or restaurants. When I'm walking I add it in quantity to my meal at the end of the day - rather a luxury as we don't use salt at all at home.
If you need rehydration (electrolytes) salts they are readily available at the pharmacy in powder or fizzy tablets. Or you could try sports drinks (but check they really do contain electrolytes, and they are not just soft drink in a fancy container).