The Colt Sporter Leather Sling was provided as a factory accessory and was also sold separately. You can see a few more details and images here: https://thecoltar15resource.com/colt-sporter-leather-sling-pn-ca10054/
In my ongoing search for Colt AR-15 accessory items that were sold individually, I found a Colt Sporter Cheekpiece that was sold on Gunbroker.com. It was basically new in the box. Unfortunately, I was not able to buy it.
I have added images and a little bit of additional information here: https://thecoltar15resource.com/colt-sporter-cheekpiece-pn-ca10026/
I have finally posted a write-up on the Colt SCW stock set. About 11 of these rare stock sets were made available to the civilian collectors market through Arms Unlimited. You can read about the stock set and see many photos and a couple of videos here: https://thecoltar15resource.com/sub-compact-weapon-scw-stock/
I have uploaded 21 photos of the Colt M203 37mm grenade launcher. See the images and additional information at this link: