I don't think you need a crib separator. I'd buy a packnplay instead. My twins have now, at 6 months, gotten to the point where they wake each other up and use each other for teething so I don't put them in the same crib together anymore . A pack and play works great as a second crib.
" I object to violence because when it appears to do good, the good is only temporary; the evil it does is permanent." Mahatma Gandhi
"This is the ultimate weakness of violence: It multiplies evil and violence in the universe. It doesn't solve any problems." Martin Luther King, Jr.