Spitfish is only available in 32-bit format.
Audacity is now available in 64 & 32-bit versions,
(if you must have 32-bit plugins, you need 32-bit Audcaity).
Here are free 64-bit de-esser plugins, (replacements for spitfish), I have used in Audacity on Windows …
T-DeEsser plus … 'T-De-Esser Plus' free VST (free crippled version)
Toneboosters V3 … https://youtu.be/5fffEP5-N5o (2 de-esser plugins, 1 simple & 1 complex, both fully functional).