The best replacement for transistor is relay.

The best alternatives to transistor are rated as following:
★★★★★  relay
★★★★  mosfet
★★★  op amp
★★★  tube
★★★  resistor
★★★  vacuum tube
★★  diode
★★  capacitor
★  fet
★  voltage regulator
★  neuron
  solid state relay
  integrated circuit
  thyristor
  semiconductor
  scr
  optocoupler
  valve
  pnp transistor

Your alternative for transistor is not listed? Suggest!
Speaking about transistor, one probably shouldn't forget about relay.

Other search terms related to transistor and their ratings are:
★★★★★ relay
★★ relay circuit
★ ldr
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Google Trends

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transistor
relay
mosfet