Well, most of the Colt Medallion grips I've seen are completely checkered rather than the double diamonds... I have a pair off of a late 80s Combat Commander I'll sell you for $12 shipped... They are a couple shades lighter than those but they are real Colt grips.
There are a few sources that will inset the medallion into any grips they sell... I'm certain Ajax grips used to do that and they make very nice grips but they'll run a lot closer to $45 or $50 shipped. Might give Pickagrip.com an email and see what he might be able to do for you... He's a good guy.
Would be very nice for a gun such as the repro but someone can correct me if I'm wrong, but if you're going for authenticity, I can't recall seeing double diamond grips with medallions from Colt.