Lens hoods minimize lens flare when shooting against the sun. Together with an UV filter the lens is also very well protected.
The 37mm lens hood shown above is offered on eBay by "hubi-77" (www.foto-tip.pl). The price is right and the quality is really good.
You need a filter on the lens (e.g an UV filter) to be able to mount these lens hoods. An UV filter is recommended anyway and it can be left on the camera all the time but if you don't want a filter on your camera there are also clear glass protection "filters" available.
Such lens hoods are called "Tulpe" (German for tulip) because of their flower like shape. Usual round lens hoods would drop a shadow into the corners.
After seeing a HF100 with a rectangular lens hood at 00:44 in this video I'd prefer such a type. It looks way cooler.
Don't follow me and buy a large 62 mm lens hood for the 0.5 wide angle converter as shown above. It will appear on the sides of the image at full wide angle. Don't even put a filter on because it will also be visible at full wide angle. I'm afraid no lens hood that mounts on a filter will work with the .5x wide angle converter.
The lens hood is not visible if you zoom in a little bit but since the display doesn't show the entire image you can't never be sure you zoomed in far enough (unless you use an external monitor).
The only lens hood that would work with the Raynox 5050 Pro is a rectangular hood that mount's directly on the wide angle adapter which has about 67mm diameter at the front.