What's the generic name for these "IBM DUAL LINE CORD PDU" thingies?
Aka a PDU that allows you to connect a device that only has one power supply to two different power sources and does an automatic switchover?
There for sure must be something cheaper than these things for 60 Euro, right?

46X4547 IBM DUAL LINE CORD PDU WITH INSTALLATION KIT | eBay.de
MPN 46X4547. The crossed-out wheeled bin symbol on the product indicates that it must not be discarded with regular household waste. Upgrade your hardware without compromise. Hard drive. The report is necessary for product complaints.