I bought a metal screw-in lenshood for my Raynox 6600 52mm. The next puzzle was how to protect the lens in transport with the hood attached. The creative solution ended up being...
Procure a large container of Clorox Disinfecting Wipes.
http://www.idsa.org/idea/idea2005/im..._closure_1.jpg
Remove the flip top . tear out the dispenser valve assembly,Rinse the lid in water thoroughly. Allow it to dry. Cement the flip top to the outer ring with Super glue. Allow to cure for 24 hrs. Finally attach to your 102mm OD round lens hood. It fits very snugly so I took the liberty of gently sanding an inner ridge on the lid with a Dremmel tool and viola! PERFECT fit for nothing!