There are several options for a 4" 1911 carry holster that run from a few bucks to a couple hundred. You can look at Fobus, Galco, Don Humme, Ross, Safariland, DeSantis, Crossbreed and many others. Your options are limited only by the features, style (IWB/OWB, open vs thumbreak, full vs strap, etc) and price you want to pay. I do know that for IWB carry a Crossbreed is tough to beat as far as comfort and concealability.
I carry a 3" 1911 and hardly know it is there. The only difference between my UC II and a 4" commander is the weight and slide length- the grips are the same so they are both easy to conceal. Personally I like the 3" as it is more comfortable to conceal the shorter slide (especially IWB) and a few ounces lighter- but the 4" is a good size as well. Just make sure you wring it out with a variety of CCP ammo to assure reliable cycling as short slide 1911's can sometimes be finicky.
"Shoot low boys...they're riding shetland ponies in search of true grit" Lewis Grizzard