I second the caution against cysteine supplementation .
There was a study that showed the same life extension from just using glycine. HED was 50g. So cysteine is not necessary.
If you want to increase glutathione you could simply take ergothioneine which increase it drastically and also increase life span by about 25%.
If you want to increase antioxidants generally, you could take selenium or selegiline which have strong anti-oxidant capacity. Selegiline also increases life span by about 25% .
And remember adding just 0.2% cysteine to the diet, abolishes the benefits of methionine restriction. So it is by no means harmless. Especially since methionine can be converted to cysteine so it's almost impossible to be deficient in it.