IMHO it seems like if one of us individually rebuilds a PS pump there's not much of a problem with the plug falling out as we don't mess with it. However when a large commercial entity (Cardone for example) rebuilds these pumps en masse they likely clean (hot tank?) the pump housings which may...
IMHO there's only one option, buy a new OEM PS pump while they're still available from Toyota. Keep and rebuild the old pump for a spare as mentioned above or sell it. You'll regret not buying a new pump once they're discontinued.
Having said that, IME these pumps (OEM) seem to last forever...