About the only reliable method is to replace half a ceiling tile with a piece of plywood.
Even that I'm not happy with; apart from the cord whip, there's the matter of the ductwork. Flex duct is the devils' spawn of the HVAC trade, and best avoided. Far better to mount a fan to the hard ceiling, and just ducting to an inlet grill in a tile.
But that's more than the customer usually wants, imagining just mounting a bath fan on a tile. Well, that's usually the equivalent of peeing in your pants - it might make you feel better, but it stinks. That flex duct has a very limited application, before the internal resistance essentially stops all air flow. All you're left with is a noisy fan that you think is doing something.