If the BNC's are loose on your toaster 4000, remove the board. Them locate two screws that secure the BNC board to the main toaster board (if you have a toaster manual it will have pictures and a removal write up). Remove the screws then unplug the small BNC board(notice where it was plug in, there are two sets of pins, one for 2000 and another set for the 4000). If look closely at the ground on the BNC connector you will notice the solder joints are loose where the case of the BNC's attach to the small board, resolder, that should take care of it. :-)
Yes there are BNC to RCA connector, I believe a set of 5 connectors came with the toaster board.
Ron