Thanks fishitlite, that does not allow power and transducer cable fit, with customizing it, per a review on Amazon. Looking for simple product that will receive both wires? Looking into grommets per jake, but no luck yet.
Electronics supply stores like Frys may have what you want. Even Lowes has some in those tall cabinets with many drawers. Ace hardware stores used to have some similar cabinets with odd items in them.
Worse case, make your own with some silicone in a PVC Pipe mold.