I guess that you could try installing the 'flip-up-via-airflow' mechanical type stall warning horn switch.
No, you really couldn't practically do that, it'd be an STC, and an expensive one at that. I find the pneumatic stall warning systems (in Cessnas) to be superior to the switch type systems anyway - I speak owning one of each. If I were to ever consider changing, I would go away from the switch, not toward it! If I thought that my flight safety actually depended upon a working stall warning system, I would rather one which is not affected by a small amount of wing ice (when you'd need it even more), and worked even with the master off - like when you're tucking the plane into a tight spot forced landing, after turning the master off in your pre forced landing checklist...
It is permissible to approve a certified plane with "buffet" being the only stall warning - no stall warning system. I have flown a certified single engine turbine plane which had no stall warning system, just buffet, as well as various "Cubs", Tiger Moths, and other vintage planes. But, I agree, if equipped, it should work- If it doesn't work, the plane is not "airworthy", and should not be flown.
Yes, the switches are astoundingly expensive, but they're not a regular microswitch, they are specially made for that application, yes, I'm sure, with high product liability costs.....