Hi John
I purchased a Molex 3 pin connector to mate with the Lionel brick's plug. I simply ran the outputs from the Molex to the input of the NCE 10 amp booster. I believe some call the 3 pin Molex a motorcycle connector. I don't recall exactly who I purcheased the 3 pin Molex from on eBay, but I found similar male and female ones on Amazon. Recommend you read the thread referenced in Mikes' thread above for a discussion about the role of the 3rd pin in the connector. It doesn't carry current but serves in an interlocking role.
Ed