If you really want something like that, it is not too hard to construct. I built a speaker pod recently to relocate the driver's side stereo speaker to a better listening position. This was my first fiberglass enclosure project. It was time consuming, but pretty easy.
Start with a ring in which to mount the gauge. Then, cut a base. Use dowels and other cut wood pieces to get the mounting ring at the right angle and attached to the base. Glue everything together. Buy some stretchy material at a fabric store (or use an old t-shirt) and stretch it around the ring and base starting at the ring and attaching it to the bottom of the base with hot glue. paint it with resin and let it dry. Repeat. Next, cut some fiberglass strips and apply them to your mold with resin. Build it up gradually. Obviously, leave the center of the ring untouched. You will cut it out later. Next, apply bondo over the fiberglass mold. Sand smooth. Finish with paint, vinyl or carpet (depending on what you're making.
I'm sure someone makes a gauge pod. But sometimes the marine stuff is just odd-sized enough to make custom fabrication necessary.
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Red 1998 Closed Bow Ski Boat, PCM GT40, 310 hp, Standard Gear Reduction, Acme 4 blade, Perfect Pass SG/Zbox.
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