Shrug, get you one of the rubber fuse connectors for blade type fuses that has the little rubber cap to seal it. Wire it straight to your cranking battery. Then solder and heat shrink your power wire to it. Seperate wires to your finder makes sure you have enough voltage and current to the unit and less chance of picking up interference.

ATC and ATO Waterproof Fuse Holders - Inline

Some auto parts places carry these.