This place does the right style badge cut-out for a NCIS badge on a Belt Badge clip. Belt Badge Clips DOUBLE THICK STYLE
It also does the Credential cases with the badge cut out but remember most replicas are a slightly different shape and not a snug fit.
I have also been looking and while authentic badges are not for sale, there are some pretty convincing replicas out there. Here is one that I found recently. . .
See if you can find the Strong Leather cut out for it via their website, then contact a retailer. You WILL feel and see the difference in the prop versus buying a no name clip.