I have a ryobi vacuum with the lower bung on it to empty it out. (this one at bunnings)
Its quite common in the US for there to be pumps that go onto that to let you drain the water as you are vacuuming out to somewhere else, so for like waterblasting a concrete floor in the basement, not having to stop and empty the vacuum every 5 mins.
But asking locally I get nothing.
USA has https://www.amazon.com/Vacmaster-Wet-Pump-Accessory-PE401/dp/B00NR8K5KW and https://www.homedepot.com/p/RIDGID-Quick-Connect-Pump-Accessory-for-RIDGID-Wet-Dry-Vacs-VP2000/100496507 for what I consider a great price, but I cant find anything in proper voltage anywhere online.