The wakeboarding winches are fairly custom things. Most applications that need a winch are interested in applying a lot of force and moving it slowly, as in lifting anchors, getting vehicles unstuck from the mud/sand, lifting heavy objects, etc.
If you search Ebay or other online sales places you might find one for sale that someone has built. They aren't that hard to build and a lot of people have done their own.
If you plan on using 100volt electricity to run it the winch can be really simple. A motor driving a drum that the rope is wound up on. Get the gearing/pulley sizes appropriate for the speed you want.
If you want to use a gas engine then you need to have a centrifugal clutch, which is pretty simple. Some some old go kart and you have 90% of everything you need.