What kind of pump is It? Diaphragm? piston? or screw? If it's a diaphragm, you may be able to rob parts out of an aquarium pump. But for piston or screw you will need to find another WEN that you could steal from.
Best bet is to improvise a new coolant setup. something as simple as an old dishsoap bottle with a little plastic tube stuffed into the end of it. you can manually apply a little water by squeezing it on. Or you can make a small stand to hold it tilted to slowly drip coolant onto the wheel. I do things like that on several old mills when I need just small amounts of coolant rather than a flood.