Powering Asus 68u via DC not AC and barrel plug size

I am looking to power an Asus 68u via DC and not AC power. I plan to use a step up transformer to go from 12V DC to 19V DC. The problem is now figuring out how to go from that to the router. I am trying to find the correct barrel plug size and where I might obtain?

I have read in some places that it is 4mm x 1.35mm? Does anyone know if that is accurate?

Has anyone else powered their Asus 68u (or similar) with DC power versus AC power?

Thank you