Answered my own question. The repair stuff is called "Aquadag E": https://semicro.org/products/carbon-paint-conductive https://www.ebay.com/itm/AQUADAG-CARBON-PAINT-ARCADE-MONITOR-TV-CRT-CATHODE-REPAIR-SPARES-30-ML-BRUSH-/261808496366 Should work a treat in this application. --Chuck