you can get a metal paint that will work for that

From my '98 shop manual. Voltmeter should read about 6v with positive lead in the middle of the wire, the negative to the negative pole. Less than 6 V look for damage on the positive half of grid, more check on negative side. Have to clean around break with fine steel wool, just to freshen up the contact area, clean with rubbing alcohol, mask it off with scotch tape, have to mix that metal paint, has actual silver in it, have to put it on fairly thick apparently, overlapping the area you cleaned, may take a few coats, you can check with voltmeter. If it is a long break, it is less likely to work.