John did you manage to find the plug yet?

My spindle came a couple of days ago and the plug connector has H17-4t inscribed on it. Mine isn't the screw on type, more like a bayonet type where it needs a quarter turn. It has 2.5mm pins, so rated at 20A 500v

Searching h17 series connector brings up alibaba links only. You could try contacting them, for 1 or buy a few and put them on ebay.

H17 series circlular connector - Product Picture From Linyi City Longli Electronic Co., Ltd.