Today I opened a bottle Cazadores blanco, which should be additive free and makes this cocktail, which I already did several times before, really special. Being no friend of the salty, spicy glass rims, I used 4 drops of saline solution instead. Peychauds may be only a replacement (sorry to Brexit) but works. Next time in UK I will try to get hold of a bottle of Simon`s Margarita bitters.