Torque limiter used in Sound Voltex BOOTH cabs (i.e. all cabs before Valkyrie). Being discontinued but orderable through 2025.
Tok's official replacement is the TLEU1-618-5W which is used in Valkyrie knobs. This part has the same input shaft and torque specs but is notably 3mm longer than the TLE1-618-5W (among other differences such as housing material change to aluminum and bushing change to sintered bronze). The size difference means that it won't fit in a booth cabinet spec knob without modification.
You can order parts from Tok in small quantities direct from them, just use their contact page, email or phone to place an order.