They are are devil to get hold of as I found out when I needed some for my Custom. The nearest I could get were from the German eBay site. I was able to get some pattern ones, almost identical in fact. They had stamped on them the german TUV Tested mark so are legal in that country and an acceptable replacement.
Sorry I cannot put you on to which company it was that sold them to me but a little bit of digging around may find them.