I'm guessing you want the simplicity of a surface mounted switch since your reference a doorbell switch.
Challenge accepted....I was interested in what I might find. How about this?https://www.amazon.com/Emergency-Exit-S ... ary+switch
Dirt cheap if you can wait for the free shipping.
Another thought: If this is a 3-6 times per year event, maybe you could just insert a quick disconnect terminal inline on some exposed wire. You would have to yank it apart and reinsert but no tool would be needed and dirt cheap if you have a crimp tool already.https://www.amazon.com/dp/B000FK9X26?ta ... pcomp&th=1
If you ever get a new opener and have a torsion spring already....grab a Liftmaster 8500. Works great and no messing around with rails, chains and hanging mounts. A much cleaner install and quiet to boot.