Simple Touch Switch
The MPF102 (Q1) can be replaced with a NTE451 or ECG451, but still widely available. JFET-N-CHAN, UHF/VHF AMP.
The 2N3565 (Q1/Q2) can be replace with a 2N2222(A), BC107, BC108, BC109(A/B/C), NTE123A, or ECG123A.
The TIP31 (Q3) can be replaced with a NTE196 or ECG196, but is a common type and widely available.
The ‘Touch Plate’ can be anything non corrosive. I use a silver quarter. You can also use a small relay instead of the #53 bulb. The phone number for DigiKey is 1-800-Digi-Key.
R1 22Meg resistor
R2 47K resistor
R3,R4 100K resistor
R5,R6,R7 2K2 resistor
C1 Capacitor, 22uF, 25V
C2 Capacitor, 22uF, 25V
La1 Bulb, #53