Waterproof Rear Light

Can anyone recommend USB chargeable rear light that can withstand our northern hemisphere precipitation.
I used the moon shield "copy" that planet x sells most of last winter and it only packed up towards the end of the winter. This year I bought the moon shield and after 2 wet rides it has packed up which appears to be due to water ingress as there is condensation inside the unit. The rubber grommet was properly fitted but it obviously didn't do its job!
I would prefer a light that can used on my TT bike as well (Cannondale Slice). It needs to fix to the aero post as using the saddle mount isn't an option for me due to the Adamo saddle and lack of exposed rail.
I used the moon shield "copy" that planet x sells most of last winter and it only packed up towards the end of the winter. This year I bought the moon shield and after 2 wet rides it has packed up which appears to be due to water ingress as there is condensation inside the unit. The rubber grommet was properly fitted but it obviously didn't do its job!
I would prefer a light that can used on my TT bike as well (Cannondale Slice). It needs to fix to the aero post as using the saddle mount isn't an option for me due to the Adamo saddle and lack of exposed rail.
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Road - Wilier Izoard Centaur/Cube Agree C62 Disc
Allround - Cotic Solaris
One of my riding buddies also has one and he's had no issues either.
Do you think the comet would be compatible with the TT seat post, or just the shallower aero bike seat posts?
I read one reviewer where they accidentally out it through the washing machine and was fine.
It's not quite as bright as the superbright moon shield etc, but it is still plenty bright.
i've done this twice on the same unit
Rule #9 // If you are out riding in bad weather, it means you are a badass. Period.
Rule #12 // The correct number of bikes to own is n+1.
Rule #42 // A bike race shall never be preceded with a swim and/or followed by a run.
Thanks. It is on its way back to the supplier today for a replacement but if/when it happens again I will bear this in mind. Still going to purchase an additional light though as a backup throughout the winter and to be used on the TT next winter
Peter