Reddit reviews Topeak Fuel Tank with Charging Cable Hole, Medium

I know you already have a saddle bag and phone mount, but what about adding one of these bad boys?. Or something like this one, or even this dude.

That way, the whole works are removable, it's doubly functional, and you don't have to leave anything exposed to the elements.

A quick googling shows that weatherproof USB cables are more expensive than these bags.

Sure, they’re both from Amazon, but you are right in sizing, there are multiple offered.

Topeak Fuel Tank. This is the Large they offer. I had purchased the Medium and it’s too small for my phone.

Topeak Aero Wedge. I don’t recall if this is the Small or Medium. I like the Medium a little better because it holds slightly more and also has a zipped expansion so it can go bigger when needed.