There are a bunch of ways to instantiate a stand-off of this kind. Another option is the Nitto suite of "Lamp Holders". Here is one example:
It clamps to your bar and then holds a section of handlebar wherever you place it. The linked example has two clamps and the bar is 22.2mm diameter so any scavenged chunk from a mountain bike flat bar will fit, giving limitless possibilities. I linked the two-clamp version because that's the cheapest way to get two clamps. In my experience, a single clamp is plenty strong enough for anything, so with that "kit" you'd get two copies of it.
They offer a 31.8mm version as well as at least two different extension lengths.
Other vendors make accessory mounts in this general geometry/architecture, but the Nitto is the most stout, in my experience
Bill Lindsay
El Cerrito, CA