What humidity sensors allow the user to configure their I2C address?
As far as I know there is no humidity sensor with 3 address bits available (at least I don't know any).

Yet, you could use some I2C Mux (example: PCA9548) to switch between the different sensors. Additionally , this will also give you the benefit of lower capacitance on the I2C bus, thus resulting in higher possible speed (although this is rarely required for humidity sensors).