Good news. For as long as it lasts, there is now a source for new sector gears for the MGA Coupe window regulators. Giovanni Delicio in Obrigheim, Rheinpfalz, Germany has produced some in stainless steel, laser cut for accuracy.

At last notice the price was 110-US$ for a pair, or 60-US$ for a singe, plus shipping.
Contact the source at "Giovanni Delicio" <giovanni.delicio@icloud.com>

As of June 13, 2023 the last available sector gears have been sold. Now that the mating pinion gear has just been made available as a 3D printed part, Gio is considering having more sector gears reproduced, possible to be combined in a 4-piece kit with 2 each sector gears and pinion gears. But new sector gears will only be reproduced if/when there may be 5 prepaid orders (for 10 pieces).
To inquire, email to: "Giovanni Delicio" <giovanni.delicio@icloud.com>