I am curious if there is such a thing as a five or 10-rd POST BAN Colt 9mm AR-15 mag especially with the follower that will hold the bolt open after the last round?

The only PostBan ones that I've heard rumors about eventually turned out to be PreBan mags with plastic or wooden dowls installed so the would only fit 10 RNDS. I purchased a few of  those for a decent price ($35) !!  Other than that, I think Colt just dropped the civilian 9MM AR-15 line shortly before or just after the '94AWB so there really was not a market for 5 or 10 RND mags. LE's could get the HiCap mags and there has not been a large demand for PostBan mags due to the lack of Colt style uppers and lowers...until recently (RRA,etc.) Sorry about that...[:(]