Notes: I superglued in some aluminum wire to make the endpoints. The secondary black loop at the bottom is velcro with a bit of gaffer tape lining. The white elastic (sorry, not velcro) strap actually slides freely sideways. Given the anchor point on the opposite side, it no longer needed to exert any sideways forces on the velcro patch at the bottom.
This setup is also inherently ambidextrous, and I can swap hands whenever I'd like. The only downside is that, because it is completely non-adjustable, I had to cut several different instances of this until I had a version that fit right.