I have a couple of raised beds like these
that they like lounging around on outside when it's hot. I'm guessing getting off the hot ground and having a bit of breeze under them feels pretty good. Mine are inside 90% of the time so I've never had the need for an actively cooled bed. The ones I've had have lasted for years outside, so I guess they're pretty durable.
It's important to point out that dogs don't regulate their body temperature the same way humans do. They pant instead of sweating. The best way to make them more comfortable is to make sure there's always cool water available and make sure the air is cool enough that their panting can evaporate the heat in their bodies.