Just get 5V 3A PoE China splitters from Aliexpress.
I got the waveshare ones for the pi 4 and they're really compact. Not sure if they would work with the rock64 though
I had some luck in the UK where rpi-locator only showed the main SKU, but the sellers had “kit” stock available with a case and charger for like £10 more, on a separate page.