Poke around on the Heraldry site. They might have it or at least a better quality version to vectorize....
http://www.tioh.hqda.pentagon.mil/default.aspx
We have vectorized literally hundreds of assorted crests, DUI's, and other military insignia for the US Army over the years. This one is not one we have done though. At one point we got big order to do a couple of dozen at once in a hurry. I sent those to Vector Dr to take care of.... Once you have dozens of them done they get easier because you can often reuse elements from others to rebuild them. Also helps a lot once you start getting all of the colors nailed down. Deciphering what some of the colors should be can also be tricky. We have built up our own custom library of color names (azure, etc) or military thread colors to Pantones or custom Lab values, also Federal Standard 595C colors to Pantones, etc... a lot of work over the years. One day I need to put it all together into a nice easy to use reference and sell it.