In addition to the already mentioned Bigallet, Amaro CioCiaro is also recommended by David Wondrich.

Personally, I prefer the recipe that Arnaud's use, with Punt e Mes instead of regular sweet vermouth and more of the other two modifiers:
- 45ml Rye
- 15ml Punt e Mes
- 15ml Benedictine
- 15ml Amer Picon (or substitute)