US$ 27.80
glutathione wikipedia File:Glutathione structure.png Could NRF2 be your magic
Description
Serious side effects are highly uncommon

Direct injection into the areas of hair loss is also feasible, potentially enhancing treatment efficacy while minimizing systemic side effects
If you haven't done it already, I think it's a good idea to track down the local B12 deficiency guidelines used by your ICB (Integrated Care Board) in England (Health Boards in Wales/Scotland)

The injectable activates the systemic pathway