I have a VERY bright single-LED flashlight, powered by 2 AA batteries, rated at 85 lumens (3 watts), mostly used as a focus assist light. It is almost blinding to look directly into the light, even during daylight. I recently saw a newer model advertised as producing 115 lumens and 1 hour of runtime on two AA batteries.
Strangely, most insects and bugs seem to be paralyzed by such a bright light rather than running or flying away. It is very helpful in setting the best focus,, especially at high magnifications. I hold the flashlight with my left hand, pressed against the lens barrel, in use. Even this extremely bright light isn't enough to obtain short exposure times at reasonable apertures, but it does sometimes contribute to the total lighting of the scene. Based on a gray card exposure, this light is almost exactly the same color temperature as the Canon MT-24 flash. I cannot visually detect any abnormal tint in a gray card or Color Checker test pattern when using the light as a sole source of illumination. It does add a very small second highlight in an insect's eyes, though, which is easily removed in post.
This flashlight only uses a single LED light - the old style of using multiple LED bulbs seems to be increasingly obsolete. The flashlight uses two AA batteries, and I can obtain 45-60 minutes of continuous illumination from 2000 mAH rechargable NiMH batteries. Some heat is produced in the head of the light but nothing alarming, IMO.
The brand I use is a "Rayovac 3 watt", and it is about 14 cm x 2 cm. It may be available on the internet. I obtained it at a great price of 25 US dollars 6 months ago. It is possible to pay much more than this for a similar flashlight if one buys a Streamlight or other similar brand. Caveat emptor!