According to the BOM, PJ-079BH is a 2.5mm part, so the DC plug should match this.
There is an alternative 2.1mm (listed as 2.0mm…) DC jack on Mouser: 490‑PJ‑079AH
The center pin is +V, the outer sleeve is 0V, but all would be protected by a series diode. You can also see this printed on the case:
We found this to be a good power supply (2.5mm barrel):