A headlight is extremely useful to provide hands free light for any purpose. It is also useful for looking into mouth and eyes. Keep a headlight in your trailer and emergency vet kit. Check the batteries periodically. This is an item that is rarely used but can be indispensable in emergency situations.
Outdoor supply stores usually have a wide selection of headlights. Your vet may also have a recommendation.
My recommendation is to try a number of headlights until you find one that you like. Get the most powerful you can find (highest lumens), and one that allows you to focus the beam. Also, consider purchasing one of hundreds of free “flashlight mobile apps” for your Smartphone, so that even if you are without your headlight, you have light in an emergency.