This is the union that is in the link that zea posted:
1.5" PVC glues inside the one end, and the union nut screws onto the pump.
This is the other fitting on the same pump:
It was installed when I bought the house, so I don't know if it's a Hayward part or if it's standard plumbing. Male end screws into the pump, female end glues to 1.5" PVC. You can see the male threads on the pump, and you can put a union here if you want.
The only other leftover fittings I have in the house (from the previous owner) are these, which I have in various places on my pumps and multiports. I think they're Hayward parts, because the part numbers stamped on them start with SP. Can't read the number on the straight fitting, too chewed up:
If you want to do the unions on the pump, you'll just have to buy the Hayward part and wait. If you want to do it the other way, I'd just buy the parts from your local big box store and see if it fits. Then install standard unions and some type of valve (ball valve, pool valve, Jandy valve) to make maintenance easier in the future.
Sorry it took so long, but I hope this helps.