Cover for boat kept on water

[CruisinGA]

Just purchased an '88 Ranger 373V w/ 150 'Rude. It was loaded to the gills for '88 and has about 250 hrs on it. Everything works, and it is in great shape.

This past fall and winter, the boat stayed on the lift in our dock, but in summer the MasterCraft gets the lift and the Ranger is floating in the water attached to mooring whips.

We have the original cover, but it is about 3x as heavy and cumbersome as a cover should be and seems to be designed to attach primarily to the trailer, which is not there.

I want a cover that is has a strap to go under the front of the bow and one under the engine, and a drawstring that cinches down around the perimeter of the boat. Since we are putting this cover on while the boat is floating, lightweight material is a must.

Is this going to have to be a custom job? I have no idea what suppliers/brands of bass boat cover are worth anything. Don't necessarily care about custom cover fit, just want to keep the sun from destroying this nice condition older boat.