Tamagotchi Paradise - Missing Spring

I took apart my Tamagotchi Paradise to replace the face plate and stupidly dropped the knob.

The small spring fell out of it and disappeared on my floor.

I'm thinking of getting a ballpoint pen spring (which will likely be too narrow) and cutting it down to size to replace it.

Does anyone know where I can buy a replacement spring?

The spring is integral for performing clicks with the knob which is the only way to access Tama Labs for the store and Tama Sitter and Settings.