OldIHC

Ebay $65.00 clear or orange.

VW BUS BACK UP LIGHT REVERSE LIGHT 67-71 OEM HELLA GERMAN 211 941 073
I have to wonder if these light assemblies might work on an Old IHC. I do not know, but, maybe a double electric could be added for a turn signal.
I saw one on eBay.
Highlight the description, copy and paste to Google and see what you find. Maybe one of the VW restoration supply shops will have this.