Where can i buy a colt model 1911A1/1991 pistol in the .45 acp?

Try your local gunstores first, Jack. Your second choice should be either the clified ads in the newspaper or a pawn shop. I stray from pawn shops though, most of those guns are in there for a reason other than the owner needing money. Most pawn shop owners don't know much about how well a gun will function and you will likely be overcharged for it. As far as buying an actual Colt 1911, thats just fine if that's what suits you. But be aware that you are going to pay a LOT of money for that gun. I would advise that you go with a Springfield 1911-A1. It's modeled exactly after the Colt 1911 but its only going to cost you $500 to $600 instead of $800 to $1100. Plus, Colts are no longer manufactured in America, Springfields are. And when you get the gun, put some ammo through it, clean it regularly, and you wont have to replace the recoil or fire spring for AT LEAST 2000 rounds. Happy Shootin!