Hope it helps some one:
The drain cap assy Pentair 86202000 - 1-1/2" Drain Plug with O-Ring No.12 Image Shown 86202000 Titan RPM Plug / Inspection w/ O-ring Used on Purex, American and Pac Fab Products Manufactured By Pentair Pools Filter PartsPentair is a common name in pool filter parts. Back To American Products (Pentair) Titan RPM D.E. Filter Parts Back To American Products (Pentair) Warrior 44GPM / 66GPM / 88GPM D.E. Filter Parts Back To Pac Fab (Pentair) FNS Plus D.E. FNS24 / FNS36 / FNS48 / FNS60 Series Replacement PartsBack To Purex (Pentair) Clean & Clear Plus - CCP240

You can use a standard 1.5 PVC threaded plug found at home depot/lowes for $1.

Also another thing to use the PVC drain plugs is for replacing the broken/bad pool return jets/eyes. I wanted the water to move closer to the edge to push stuff towards the return. Drill 1 or 2 holes at an angle and screw it into the fitting. Works great and I get better aim where I want the water to go.

It isn't as pretty, but it works well and a lot cheaper.