Revert to previous Firmware (Fenix 5)

Hi all,  I realised this thread has been a bit quiet recently and the links to older firmware no longer works.

Since my Fenix 5 has self updated to version 21 it has completely destroyed the battery life of this watch.  Overnight it has changed from lasting over a week to barely 2 days even just in basic watch mode!  I have gone from loving this watch and recommending it to hating it!  All I need to do is back date the firmware which is clearly at fault as nothing else has changed.  I have been to the firmware update page on the Garmin website which only offers the next 21.71 beta version.  Unfortunately this only makes the difference of lasting a few hours longer on the battery life.  

Does anyone know how/where I can get an old firmware zip that I can use to revert this watch to it's once great self again?

Thanks, Steve