Well, you could send it to Heinie:
Heinie 1911 Sights
Heinie 1911 Original or SlantPro All Black Sights $248.75 $238.75
Heinie 1911 Original or SlantPro Straight Eight Sights $327.48 $317.48
(Same Price for Original or SlantPro Design Sights) Add $25.00 to above prices if ordering sights with wider rear notch.
Installation of 1911 Sights require machining of the slide. Turn around time for installation of Heinie 1911 Sights will take 2-6 weeks depending on blueing schedule.
(The first price is for next day air return, the second is for two day return.)
You could probably shop around and get it done for less by an independent shop.
Maybe somebody here will help you find one.
I hope this is not a real original USGI 1911, the collectors would kill a kitten if you cut up a service pistol.
You could do like I do and have a King's #107 put in the GI dovetail and a front blade staked in the GI mortise and not have to pay for milling machine time.
http://www.kingsgunworks.com/newcatalog/page02.html