What DIY methods exist to trigger a Lumix G3 without touching the camera?

I have a Panasconic Lumix DMC-G3 with a 175 mm lens which I need to trigger without touching the camera to reduce camera shake¹.

I know of the following ways to take a photo without touching the camera, however at the moment I cannot use any of those:

1. Cable release: A device that you plug into your camera with a button that releases the camera shutter.
   • I don’t own a cable release for this camera.
2. Intervalometer: A cable releases with the possibility to set up timers, e.g. for timelapses.
   • I don’t own an intervalometer for this camera.
3. Remote Release: Similar to cable releases, but they are not plugged into the camera and work via infrared.
   • I don’t own a remote release for this camera.
4. Smartphone App: Many (modern) cameras have built-in WiFi or Bluetooth which allows you to take a photo and sometimes even change settings using a smartphone app.
   • This camera has no WiFi or Bluetooth
5. PC software: Some cameras can be tethered to a PC (usually using a cable) and can be controlled and fired with some software.
   • This camera does not have tethering capabilities
6. Camera self-timer: Most cameras have a self-timer (e.g. 2 or 10 seconds).
   • I experienced that this can still cause camera shake when using a telephoto lens, about 3/4 of the images were shaky taken this way¹.

Are there any DIY methods than those described above to take a photo without touching the camera?

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^{1: My other question contains more information on the problem at hand: I’m trying to photograph comet C/2020 F3 (Neowise) by stacking images, but the results are too shaky.}