You can order just the cap at the link below however Torqeedo has a flat rate of $20 for spare parts. In addition the motor should be undated by a service center because if not sealed properly is will then cost $730 for the replacement motor.
http://www.torqeedo.com/us/en-us/pro...006-00100.html
this is the brass cap, that goes behind the shear pin...
i believe this is that helps the fishing line not wrap around and cut the seal...