Shower Mixer
From Amazon
GROHE Grohtherm - Thermostatic Shower Mixer Trim Set to Control 2 showers - Concealed installation for GROHE Rapido SmartBox (35 600) - Safety Button at 38°C - Metal Escutcheon - Chrome - 24079000
Wayfair
GROHE Grohtherm Thermostatic Shower Mixer Trim Set to Control 2 Showers