Forward Height Adjusting collar...
Dennis, look at the thread right above this, and the one right below this thread. There is a Parts List above it and one titled Ouch.... below it. They have a listing of what companies I know of that hopefully will have parts you are looking for. Also check the Technical Resource Library (TRL) by clicking on the link to it in my signature element. It is always there. Good luck and let us know if you find what you need and where.