Is it possible to purchase only the head portion of WL Limit Switch?

Yes, replacements are available.

Head and Actuator

Example:

Set

WLCA2 Limit Switch

Head and Actuator 

WL-1H1100 Limit Switch

Head without Actuator

The model numbers for Heads without Actuators are the model numbers for Heads with Actuators minus the numbers after WL-[]H. 

Example:

Set

WLCA2 Limit Switch

Head without Actuator 

WL-1H Limit Switch

Rotary Lever Actuators

Example:

WLCA2 Limit Switch

Actuator 

WL-1A100 Limit Switch