This plug should fit most of the regular garden pumps.

It has a G ½ thread which means if your pump thred measures at around 18,6mm in inner diameter you should be good to go.

I also added some space behind the thread for an o-ring for proper seal.

DO NOT OVERTIGHTEN!!!!

If you overtighten the plug it will sheer along the layer lines and you get the thread stuck in your pump.

If this should happen, you can remove it pretty easy by heating a large screwdriver and push it in. After it cooled down you can simply unscrew it.

And remember to let the water out of your pump before winter ;)