Replacement transformer for McKeller Drill?

I have a McKeller 14.4v drill/driver, which works fine but the transformer for the charger is defective (cable broken inside). Due to design of screwheads I cannot open it to try a repair and Focus no longer stock McKeller. Does anyone have a replacement transformer or could I use an equivalent from another make? 230-240v ac primary / dc17v 400MA 6.8 VA secondary.