Just posted on FB. 

I managed to get it all reassembled and the switch is working ok. I was playing with it a bunch and maybe every 20-30 "toggles" the switch gets a bit jammed. Normally just pressing the switch again fixes it, but one time I had to take it out, manually push it, and then it was good again.

In case anyone stumbles across this the spring I ended up choosing was "BB-31CS" (https://www.digikey.com/en/products/detail/century-spring-corp/BB-31CS/11671413) which is:

OD - 0.105" (2.67mm)
Length - 0.280" (7.11mm)
Spring rate - 0.86 lbs/in

Terrapin. I'll shoot you a message because having a backup would be good anyway

Probably going to have to contact the guy on FB market Place directly.

Oh shoot I misread Terrapins post. I'll reach out to them on FB

Yeah Harold is the guy with the parts. hopefully he still has it. It sounded like just what you were after and a decent price too.