In the interest of soft robotics I need a high power programmable battery power supply. I also found this.
They do not have 100kV batteries. They use 12-volt batteries to power a fancy dc-dc converter, which steps up the voltage to 100kV with a Cockroft-Walton voltage multiplier. Ref: the abstract of the article you cite.
EDIT (response to comment): I read the material at artimusrobotics.com and read two of their papers in Science. Those Colorado guys are clever, but they're fighting the classic battle of high-voltage electrostatics vs high-current electromagnetics. From this I conclude that HASEL is not practical for operating a human-size bipedal robot, at least not this decade.
Use ordinary electric motors instead. Read about the actuators developed for the MIT Mini Cheetah.