Need help with antique piano

My wife’s aunt gave her an antique Aeolian Player Piano but the key to lock the key cover isn’t there. We have little ones and would like to be able to lock it to prevent them banging around on it all day and smashing fingers. Where would the best place be to find one?

I’m unsure the model/serial on it and wouldn’t know where to find that either so any help would be appreciated. I know next to nothing about pianos other than they are heavy as hell.