Looks like Iseli nursery is growing it. Get with your local garden center and as them to special order one for you if it interests you. Be aware that, with an annual growth rate of 6 to 8 inches, 'Horstmann' is far from being a miniature. Definitely an intermediate.

After 10 years, it says 12 by 8 feet, and it definitely doesn't magically stop there.

Cedrus take quite well to pruning, but it's something you'll probably need to do 2 to 3 times a year.

Picture of one maybe 20 ft. tall has been shown on this site on the past. But blue cedars can readily be pruned annually to control size without spoiling them.

I've seen a few Cedrus atlantica 'Glauca' pruned to stay quite compact so I assume they take well to pruning.

Just an idea if you want something that grows slow. Cedrus atlantica 'Sapphire Nymph' grows quite slow. Mine has steadily grown a few inches a year for the 6 years I have had it but I have seen varying growth rates in photos. Some look slow like mine while others have a faster growth of maybe 3-6 inches. So many variables. If left to it's own accord it will be a squat spreader but it looks like a lot of nurseries are training them upright with a central leader. I'm sure that you could easily prune either to stay dense and compact.

I have one, probably from Iseli. It is certainly slower growing than the species, but as noted above, they take very well to pruning. It's a nice specimen. I've never yet pruned it but expect to. I have never pruned cedars more than twice a year, but they certainly are ready for it when I do it!