Unfortunately there isn't. The only item similar is the Focus Band, which does leave a Pokémon with 1 HP remaining when hit by an attack that would otherwise KO it, but rather than requiring the holder to be on full health and working 100% of the time when the requirement is fulfilled, it instead has a 10% chance of working regardless of the holder's health.
tl;dr no
it is a item that you obtain in pokemon soul silver that you use to catch lugia the legendary bird in the whirl islands.
What exactly is a 'moss stone'? It's not an evolutionary stone, and the closest item I can think of is the moss rock in Eterna Forest, which isn't in this game...
What? Is that even a item in Pokemon silver or the others?
The Mist Stone was a fictional item thought up by fans during the Red/Blue days to explain a number of Pokemon that evolved from already fully-evolved Pokemon. There is no item by that name in any game so far. Are you perhaps thinking of a different item?
In pokemon soul silver you get the item finder (dowsing mchn) in Ecruteak city. An ace trainer will give it to you. He is in the house on the left of the pokemon center and right of the gym. Hope this helped.
Focus sash is not an item in Firered. It will later appear in Diamond and Pearl.
you need the silver wing key item
it is a item that you obtain in pokemon soul silver that you use to catch lugia the legendary bird in the whirl islands.
Focus sash
you cant be one hit k.o.
It is a hold item that doubles the pokemon's attack power, but makes it confused. The item is used up, and dissapears.
to get a lucky in soul silver you have to catch a chansy and then take the item if it has a item
What exactly is a 'moss stone'? It's not an evolutionary stone, and the closest item I can think of is the moss rock in Eterna Forest, which isn't in this game...
That item is only available in Pokemon Diamond, Pearl, and Platinum.
There's no item known as the Darkness Key in Pokemon. At all.
Just make one of your Pokemon hold the item and clone(duplicate) it.
The second item you need is the title bell.