A waterproof box with a built in power bank can be a perfect solution for your mobile power bank demand.
Here below is a sample for you. (copyright of this product and pic owns to our customer exclusively)
Waterproof hard case protects the inner power bank perfectly by keep it functional in variety circumstances. Pic: Waterproof storage case X-2002 used for power bank package.
Also our waterproof hard box/ waterproof hard cases can be used for packing other electronics or anything that's wetness sensitive.
To know more about our products, please click the link to view our website www.plasticboxplus.com