I had gliderpilot’s preload switch 3D printed for me by a local guy for a small fee.
I like it because its one handed operation. “Clear Prop!” Twist the knob a bit, wait for the ESCs to beep then turn it the full 90 degrees. The disadvantage is you need to disassemble the main switch and reassemble with the new knob and wiring.
The other way to go is to wire a resistor through a separate momentary on switch. Hold it down, wait for the ESCs to beep, turn either main switch to on, then let off the momentary. It’s two handed operation but you wouldn’t have to disassemble the switch.