Hydraulic mtb-style brake lever on drop handlebars tl;dr

Does anyone know of an existing hydraulic brake lever (eg (like this)) that can clamp on a 31.8mm bar or can anyone think of a way I can hack/bodge/modify one?

I'm thinking similar to how CX bikes do it with cables except I want it not inline (separate brake) and hydraulic

Context:


I only have a right hand
I'm building a road bike with drop handlebars and a hydraulic disk brake (Shimano r8070, right-side, front brake).
I have been happy with a single brake for 20+ years but since having kids I feel like a second, backup, brake would be wise


Out of the box solutions welcome!
Shimano's new GRX line include "sub-levers" that seem to fit your needs.

They are meant to be mounted on the tops of drop bars near the stem and run along the same hydraulic line as your main hydraulic lever/shifter. The product ID I believe you need would be BL-RX812-R (or -L if the left was desired)



https://bike.shimano.com/en-EU/product/component/grx-11-speed/BL-RX812-R.html