I supose it is possible but I'd be sceptical about the casquette/nacele. Indian Sales Corp probably had a contract with Royal Enfield that wouldn't have allowed a sale like that. The old Indian Sales REs have all been in someones garage or junk pile for the last 45 to 50 years and a lot has happened to them since then. My Trailblazer came with a front fork off of a G model RE from the early 50s when I bought it in the early 80s. Since then I've found all the original Traiblazer front end parts. It was a lot of scrounging by snail mail, telephone, and thank God for the internet. Some of the hardest parts to find came from E-pay.
I have also collected parts for the Apache, Chief, and Tomahawk models along the way. The Tomahawk 500 twin had the inclosed head light casquette that you mentioned. I would figure the one you have probably came from a Tomahawk.