Where you see a NPN transistor in a low-side switch configuration like this, you can usually replace a N-channel MOSFET.
The "base" of the NPN becomes the "gate" of the MOSFET.
The "emitter" of the NPN becomes the "source" of the MOSFET.
The "collector" of the NPN becomes the "drain" of the MOSFET.
There should be a 10 kOhm - 50 kOhm resistor between gate and source.
There doesn't typically have to be a resistor at all between control pin (on Arduino) and gate, so the base resistor can be removed. If you want one to limit outrush current when switching, 100-150 Ohms is sufficient.
Or just buy the NPN transistor they're using in the Arduino example and call it good. Efficiency likely won't actually matter in this case :-) Jameco or Digi-Key ought to have them. Just change the 1k base resistor to 150-200 Ohms; 5 mA is way too little base current for driving a 1A solenoid in that circuit.