I like these myself, and this USB-C one would work fine for your use.

Amazon.com: DC DC12V-24V to 5V 3A Micro USB Buck Converter Module Step Down Power Adapter, Application with Ring Alarm Keypad : Electronics

There are different variations depending on how you want to wire it.

I'd pull the wires off the old panel and connect them directly to a 12V power supply.

The power supply provided in the box say 27 watts but has 5v at 3A (15w) or 9v at 3A (27w) in the fine print. It actually says or. Here is a list of usb C step down converters I have tried. The hiletgo unit did not even produce a light in the eero at any voltage.

HiLetgo 2pcs LM2596 Adjustable... https://www.amazon.com/dp/B00LSEBYHU?ref=ppx_pop_mob_ap_share

PlusRoc Waterproof 12V/24V to 5V... https://www.amazon.com/dp/B09DGDQ48H?ref=ppx_pop_mob_ap_share

Quick Charge QC3.0 USB C... https://www.amazon.com/dp/B0B212GFM9?ref=ppx_pop_mob_ap_share