I remember my first NEO AES came with a 12v 1A transformer in the box, said on the base to use PRO POW E, the revision of that i dont know cause i sold it many years ago, the AES i have now says use PRO POW 3, and its a Japanese console. Ive been using the Sega Mega Drive 10v transformer on that.
Just a note since i saw someone ask about the amp rating on a transformer, the rating must be the same or higher than required, the rating 5v 3amp doesnt mean its spitting out 3 amps all the time, it means 3 amps is the maximum it can supply at 5 volts, so using a transformer with a rating of 4 amps is perfectly fine, cause it can easily supply the 3 amps required with abit more headroom there.
You can use a power supply that is rated 30 amps if you want to, as long as the voltage is correct. The machine wont pull more current than it needs to do its work.