Please don't ask why I know this ... 
But the simple & cheap answer to restore the cams waterproof rating is to get a flat 29.5mm 'mineral glass watch crystal' (ebay can be a good source) add a bead of silicone to give it a seal, gets one out of trouble.
The IR glass cover looks to be the same size.... just in case, lol

But the simple & cheap answer to restore the cams waterproof rating is to get a flat 29.5mm 'mineral glass watch crystal' (ebay can be a good source) add a bead of silicone to give it a seal, gets one out of trouble.
The IR glass cover looks to be the same size.... just in case, lol