I think there's a capacitor in there that stays charged when the light is "off". Also some clever circuitry that lets pulsed power through to keep it charged but not enough to put the light on.
Or something like that!
I'm amazed you're not making them yourself!
Something like this? They make to order:
https://www.silverapplewood.co.uk/products/solid-pine-spice-rack-5-tiers-shelves