We use one of these, about $12 from Amazon. It's cheap (in both senses of the word) but checks all the boxes. Not a bike light but it's very light weight and has a handle you could attach with a carabiner or somesuch.

You can cycle through all the light colors but a long press will turn it off or on without changing the color, and the remote makes it easy too. It has to be recharged every several days.