Power Supply for Acceleport 16em


I have four (4) Acceleport 16em RS-232 boxes in a row connected to a PCI-X host adapter. I have a power supply (Part-Nr. 10000895E) connected to the third box in the row and no power supply connected to the last box in the row and have been using this constellation for over 6 years. Recently, I experienced malfunctioning which could be resolved by moving the power supply from the third to the fourth box. I re-red the instructions carefully and they say that both the third and the fourth box should have their own power supply.
Q1) Is this correct? Do I need two power supplies for running four Acceleport 16em RS-232 boxes?
Q2) Where can I get an additional power supply (Part-Nr. 10000895E) ? The digi page doesn’t offer it anymore.