As shady as this might seem, I zipped an extension I downloaded from the Chrome Webstore once and uploaded it here:
https://file.io/alT1WhF92AMO
While Chrome recognizes it as violating the web store rules,
View attachment 124988311
it's still fully functional and transferable to other Chrome installations. When navigating to chrome://extensions/ you can unpack it via the top left button there.
Afterwards, on any Onlyfans page or chat with media in it (except not unlocked PPV content), you'll find the download buttons next to it, like this
View attachment 124988811
Hope it works for you!