I also have not been able to locate a board mount “B” USB male connector. What I have located is a USB “B” male connector in a circular housing with a 1 meter pig tail that could be hard solder to you distribution board. You would need to devise some sort mounting board to make it work.
Click here for the connector web link
This may also be a more durable solution as if you had the male connectors directly connected to a mother board, any misalignment in the mating cycle could possibly break the board.
The technical reference number is T4172054
