This grid from Lightbulb Rentals is specifically designed to fit the Profoto Magnum Reflector. It narrows the beam spread of light to 10deg.
Profoto Softbox RFi Octa: Front Diffuser (3′)$30/day
Profoto Softbox RFi 4 x 6′: Bag$40/day
White Umbrella (24″)$5/day
7″ Honeycomb Grid 10°$5/day
Profoto Prohead Extension Cable$25/day
Profoto Softbox RFi Octa 40° Control Grid: Bag (5′)$20/day
Profoto 7″ Grid Reflector$10/day
Profoto Prohead Plus Strobe Light$30/day