I would suggest that you could reclaim your existing sump by use of a Helicoil rethreading kit. This would return it to standard which would mean a standard sump plug could again be used. This repair would preferably mean removal of the sump to catch the swarf etc, I think most small engineering shops or competent garage could do this, much cheaper than a new sump. The process essentially renews the thread, I am sure there are other brands of thread insert available but a search on the net will soon establish that.
