An in-between area is component clubs.
From 1994 to 2008, I played Ping Eye2 clone iron heads, the Pro Tour Blacks. The clubs were custom-fit for me by a small club shop down near Dallas, TX. The lie was 2* flat, and the irons were shafted in True Temper's Dynalite Gold S300 (the high-launch cousin of Dynamic Gold, the low-launch shaft).
The iron heads were quite durable - I played a $5 premium per head for these irons over some other available heads. Through the years I hit some rocks with the heads, but the heads showed minimal denting or anything. Supposedly in the late 1990s Ping won a lawsuit against Pro Tour, and all unsold clubheads had to be melted down.
I met dozens of other golfers during the 1990s who also played the Pro Tour iron heads.
Main reason I dropped the clubs was in 2008 I couldn't bend the shafts any more. I had lost about 15 yards per club in distance, and had ruined my swing tempo trying to hit the ball harder. So, I went to regular-shafted clubs (except light-stiff wedge flex in my GW and SW).
Once you get past the year 2000, a lot of these custom club shops faded away, especially in big metro areas.
Some of the component club sources include the Maltby line from GolfWorks (now owned by Golf Galaxy), and the Snake Eyes line from Golfsmith. Maltby/GolfWorks has its own R&D operation, and also rates new irons each year from the major OEMs in the Maltby Playability Factor system.
A lot of the custom club shops will find an open-model family of iron, metal wood and wedge heads from different golf equipment foundaries. These models are fairly stable from year to year, and can be customized with the shop's label, or for a label used by a group of shops. The best way to see what's going on is to find a small custom shop, and talk to the people who run it.
Also, talk to the shop's customers. If you find out several of the area's serious golfers use clubs made by the shop, chances are you've found something.