I have noticed that none of pokemons found on Moon carry any kind of item:

 

 

My suggestion is to put a 1-5% chance to encounter pokemon with moon stone. It's not like we do not have enough source of moon stones (we can fam them from nidorans, glooms, etc.), but to make logic right - what would be better source of moon stones than moon itself?

If there were moon stones on the moon I'd be swimming in them already. I've caught over 300 Clefairies/Clefables looking for the right one. :confused: Though I was always curious as to why there weren't any there so +1 to the idea.

I think this is a coherent and good idea, it can't ruin economy since the input on moonstone wouldn't be that large with what you suggest (low chance of getting it on some pokes)

256995 I've caught over 300 Clefairies/Clefables looking for the right one. :confused:

Oh boy, I hope you're using synchronize pokes xD