Improve existing plastic housing for consumer electronic product

We have an existing working prototype of a new consumer product. Before we go into mass production we are seeking experience industrial design with plastic enclosure experience to improve the overall design and ensure the housing is waterproof to IP67 or IP68 (preferred). The housing must be designed to incorporate and existing PCB and battery system. There is also a USB connection that needs improvement to meet these ingress ratings also. There must also be a waterproof button designed into the housing to activate a momentary switch on the PCB. There are strict limitation on diameter and height of the product. Consideration must be made also with breathable vent to manage any condensation issues although this is not essential. Experience with ABS plastic design and silicon rubber is regarded. STEP or similar files can be provided as a starting guide. Solidworks is preferred as this is the only CAD package I have available however this is not essential.