There is also
this barrel adjuster that I like.
When I looked for an inline barrel adjuster, that is what my bike repair shop suggested. You slide it in the hole and it works like a normal screwed-in adjuster, except it fits in a non-threaded hole and the two stops keep the adjuster in place. Quite easy to use with only one hand.
I installed one on my tandem to help adjust the rear brake. The normal adjuster installed near the brake is way to far back!