External Power Supply HD Omni Thunderbolt Core



Where can I buy an external power supply for HD OMNI Thunderbolt HD?
I want to use HD Omni Thunderbolt with adaptor to USB-C Thunderbolt 3.
It is a bus-powered adaptor but I'd feel much safer using an external power source.

Mine didn't come with a power cable for some reason, where can I buy just the external power by itself for the HD OMNI TB Core unit?