The Cavision clamp on lens hood was $60 last time i looked. It's an easily mounted screw clamp, the shade is pliable rubber which is nice.

Van Dieman, True Lens Care and Formatt all make clamp on sunshades and rotating filter holders. There are some cheaper sources as well. Do some searching.

I wound up with a Cavision 4x4 bellows as well as the Cavision clamp on lens shade.