I have several of these. They're durable and have no battery, which is a bonus. I use separate, large batteries, which all have 2 or more USB ports. Some of the fans with built-in batteries can't be used when the battery dies and you start charging. One of the ones I tried had battery charging problems. They're also heavier, which makes clipping them onto things more difficult.
The most effective way is to use a chiller, but they can get a bit pricey. I use frozen water bottles during the day when the lid is on and a clip-on fan when I get home!