The contactors in a battery pack need to be able to switch high currents and high DC voltages. Hence they tend to be specialised discrete components. The following is a list of contactor manufacturers
Eaton
A power management company that has been in business for more than 100 years.
Company URL: eaton.com
Gigavac
All high power relays and power contactors are designed and engineered at their facility in Carpinteria, California.
Company URL: Gigavac.com

Schaltbau
Designed to IEC specifications, our wide variety of AC and DC contactors in stock range from contactors for low-voltage devices, such as batteries, through to high-voltage power contactors up to 4,800 V and 1,100 A.
Company URL: schaltbau.com
TDK
A comprehensive electronic components manufacturer. Their HVC series can be used in a wide range of applications, e.g. DC fast charging stations, renewable energy storage systems as well as battery disconnect units (BDU).
Company URL: TDK.com
TE Connectivity
Design and manufacturing sensor and connectivity solutions for data, signals and power systems.
Company URL: te.com