Colt doesn't make any "aftermarket" parts for AR's. Aside from the bits that come with special models ie. the scope, mount, and cheekpiece that come on the Delta HBar, etc... (which are colt marked aftermarket add-on parts - and which are usually just made by other manufacturers and marked with the Colt logo), I'm afraid you'll only find "standard/stock" Colt replacement parts on the market. Don't fret though, as there are numerous reputable companies out there that make the parts that you are looking for (ie. PRI, etc...).