What kind of power plug is that on my laptop?

I have an Acrobat 80486 slc / 25 laptop in my collection. Unfortunately, I can't find a suitable power supply to get the 12.5 volts 25 watts.

Does anyone know what kind of plug it is so that I can build my own power supply.

What should it be: 12.5V / 2A… A power supply from an old router with 12V and 2A should be sufficient!

But I don't know what kind of plug it is. I know what kind of power supply I need.