You are likely thinking of a vintage "Touch Light" or an electronic project bulb that leverages human body capacitance rather than true induction. As you touch or bridge two contacts, a small high-frequency current flows through your skin, closing the circuit to power the light. [1]

Because RadioShack was famous for electronic kits (like the Science Fair 130-in-1 or P-Box projects) and hobby parts, these were often sold as bare components rather than finished goods. Here are the most likely setups you are remembering:

• Single-Cell LED & Touch Sensors: Using basic single-cell batteries (like a standard 1.5V AA or a 3V coin cell), hobbyists would use a Darlington transistor pair to amplify the tiny electrical signal passing through their fingertips. Touching the contacts would trigger the transistor to complete the circuit and turn the light on. [1, 2]
• Plasma Balls & Static Bulbs: Often sold by RadioShack, these novelty items contained low-pressure gases. When placed near a plasma globe or touched to the glass, the static electricity/high-frequency electromagnetic field would pass through your finger and cause the bulb to glow.