Hell, with all the things that have been done to 1911s over the years, why not just have a gunsmith install a set of genuine M1 Garand sights on your slide?
There are a number of types of adjustable sights (not SITES) for the Model 1911 and copies. Check www.brownells.com for a look at some. None have the M1/M14 deal where elevation and windage are on opposite sides, though. And of course none are that large.