Got this torque wrench adapter at work earlier via Amazon. Motion Pro 08-0380
Its basically a clamp with a 3/8" drive input meant to hold normal wrenches as an alternative to dedicated crows foot and square drive box ends. The machining is mostly clean and it has good tolerances on the drive broaching. One screw doesn't thread quite as easily as the other but they can both be set finger tight, you don't really need an allen key. It did come with a packet of white grease that I haven't tried yet.
With a small 8x10:
With a larger 22x24. KTC M150 series with relative flat edges:
Vintage Proto with rounded edges, holds just as well:
There is a little bit of play with a tapered handle if you push on it (no duh) but it won't rattle or fall out on it's own:

It can even grip some smaller round bars. Crazy example with a 1/2" extension:
Example usage mounted on a torque wrench:
A little pricey for what it is and probably not perfect for every situation but it takes up way less space than a full set of dedicated torque adapters and I'm sure I'll be glad to have it at some point.