man thats a bummer, can you get a good photo of it Dicko?
i have seen tapered sump plugs for when this kinda thing happens, they also cut their own thread, and have another smaller o'ring sealed sump plug in the centre of them, screw them in with loctite or jb weld and its as good as new. http://www.cgenterprises.com/drain_plugs_oversize_repair.htm
If it were me and didnt have alot of dollars to get this fixed "right" i'd defently be trying this fix first. At the end of the day the only other way i see to fix this is to remove the motor, and use a wel on bung with new thread and sealing serface....
Keep us updated.
Regards Andrew