Rajio Showa Rider
^ This ^there is only one dx lost driver so just get that... as for the joker memory, look for the T2 joker memory that came with that figure-oh magazine. since it automatically does the henshin sound after it says "JOKER" and youll get the proper maximum drive sound.
Here's a Yahoo Japan search, which is your best bet at getting a T2 Joker Memory. Contact your preferred Middleman to get