Ugh, I feel you, it's so frustrating when a specific brand suddenly disappears from the usual stores! Have you tried calling other Mercury branches or Watsons directly para malaman if may stock pa sila? One of my mum friends managed to find hard-to-find vitamins by asking the pharmacist kung saan pa available locally or if pwede i-order online through their website. You could also check Lazada or Shopee, maraming legitimate sellers doon ng vitamins, though make sure verified seller lang para safe. Hope you find it soon!