Peter
Suggest you contact Austin Weltman, ACOC member for many years, he used to be ACOC official registrar for Acecas, During which time he had various spare parts made including front and rear twin bumper sets. ( I think they were made in Stainless Steel.)
He may well have a spare set of end caps or still know where to get some reproduced, you've got nothing to loose.
Austins email:- Austin at austin 100 dot plus dot com
**** please note the Plus is plus not the plus sign (+)
Keith