Assuming this
picture of an MST brushed ESC is correct, that is what is commonly known as a "Dean's plug." You can buy batteries easily with that pre-installed such as
this one.
The only other thing I would add about the MST cars is they are highly regarded in the (small) RC drift world but I don't know if there is a store in America that carries replacement parts readily. In that community, self-importing parts from Asia screams "authenticity" but for you it might equal, "inconvenient." If you do go that route,
this store is one you should bookmark for starters. The Tamiya cars are on a commonly shared platform - if you don't have a place local to you with parts for it on the shelf, they should be able to get them for you pretty quickly or you can order them yourself just as easily.