Can I wire these automotive peltier heating/cooling devices as on/off without a temperature controller?
I'm not familiar with the specific seat but in general, there is no problem powering TEC modules without a temperature controller. This motor controller would be a suitable way to deliver variable voltage DC power to the TEC and reversing the direction of the current flow to get either heating or cooling. You can connect a resistor in series with the potentiometer to limit the maximum output voltage that can be set when you turn it to its maximum clockwise position. This will also generate no additional waste heat in your work space.

https://www.amazon.com/Potentiometer-Switch-Control-Driver-Controller/dp/B07KJXG7F5