Speedlight modifier for bird portraits suggestions

Will be going to an event where rescued birds and other animals will be posed by handlers. Handlers will give the thumbs up/down to the use of flash for each critter.

The event will be held between 10-1pm local time, probably in open shade or no shade.

What types of speedlight modifiers have you used/recommend for this?

I'm thinking of using something like the Neewer Octagonal Studio Softbox Flash Diffuse
Thx