Try a small mirrorless or P&S camera that's easy to handle one-handed. My favorites include the V1 and Ricoh GR.

But any of the 1 System cameras or Ricoh GRD (smaller sensor) models would do. All have excellent handling in one hand.

And any compact camera may be improved with a Flipbac or similar finger grip extension. I put one on my V1. Much easier handling without adding bulk or weight.

Another factor is quick autofocus and shutter release response. But the gap has closed over the years and most mirrorless cameras are pretty quick and responsive now.

The Olympus Tough cameras are weather resistant and pretty quick too. A friend had one and the only change I'd make would be to add a Flipbac finger grip.