Not sure about commercial products but there is absolutely no reason they can't exist with an adequate heat sink. 5 watts isn't exactly a lot of power and as long as that power is transferred with little loss to an antenna then even small heat sinks can be used with almost bulletproof performance. All comes down to the output transistors capabilities. Anything grossly overspecced for high wattage will run cool without a fan at <5 watts of power and I think some commercial units might switch off fanning at low power or have some fan heat sensor.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~