You’re not gonna be lining a flexible handheld device with the kind of solar panels that can achieve such efficiencies even under ideal conditions. If you want an actual parasol rather than an unwieldy, rigid, parasol shaped bed for a bunch of solar panels, this is a job for the more alternative solar cell types that are cheaper and less efficient, but can be made thinner and lighter, and can be stuck on something like that. Unfortunately those generally have piss poor efficiency and they degrade to near uselessness very quickly.