There's the Jetbeam RRT series, Eagletac M series, the new Sunwayled M series, Surefire U2, and a bunch of others.
Use the search feature, all those options and hundreds more came up just by searching "control ring" on the CPF search box, as well as several other threads asking the exact same question.
Is there any control ring that allows to control the speed of the ramp-up/down ?
Something like:
Turned completely to one side for fast ramp-down, other side for fast ramp-up.
Turned slightly to one side for slow ramp-down, other side for slow ramp-up.