Lots of manufacturers making Scouts today, in every price range: Savage (2 including an Axis), Mossberg, Ruger, Steyr. The range is pretty well covered. I personally think the original Savage Scout offers the best value for the dollar, but they all give you the chance to try the concept out for yourself.
Building one yourself, or having one built for you, is unlikely to be cost-effective compared to the factory offerings; but we are
gun nutz, after all, and having exactly the thing you want (and knowing that it is unique) is certainly a valid reason to do it.
One thing, though: it would be a shame to get too hung up on the exact, precise parameters laid out by Cooper when he pioneered the idea. So what if your gun is a few ounces too heavy, or a half-inch too long? It's
your gun; do it up the way you want. I always laugh when some guy comes on the Scout Forum, shows a really nice rig that he has assembled to his own specs at great expense and effort...and then somebody pipes up with "Nope, sorry...that's one quarter inch over length. No good!"
