They are currently made by C-more systems. but it is my understanding that C-more is not happy with things at colt (something about money, or lack of it) so dealers are having difficulty getting these anymore. I like mine, I recently purchased one. I had been given a cheapy chinese 4x carry handle scope, it now holds a closet door open.
I have an assortment of optics from Nikons to Leupolds to Aimpoint. I think this is a good scope, you dont have to buy any other hardware to mount it on your rifle, it is nice and compact. The optics are clear. I dont regret buying it at all. now I would love a ACOG, but I will also keep this optic, I like it for what it is.
Your other choice is to buy a ARMS carry handle mount ($50), rings ($20 to $100 depending on brand and qaulity), and then a scope.
Just my .02 worth