I have around three or four shunt regulators for use on nominal 12 volt systems. They are on PCB's and include the LM 723 and 555 IC's - ex Chris Greacen design.
I have since upgraded to Ghurd's dump load circuit so the above items are no longer needed.
They are going for FREE by airmail to anyone in the world either as an entire batch, or, one by one, depending on the mumber of e-mails I receive.
A circuit drawing will be included.
My e-mail (change the obvious) is strltdATnetvigatordotcom.
Make sure your postal address is correct.
David in HK