Possibly SMD packaging isn't large enough to accommodate the larger surface area of a varicap junction. That's just a guess though.
Some other devices also show large capacitance changes, for example some LEDs, might be worth experimenting. I would anticipate most 'super bright' LEDs having similar characteristics as it is the fluorescent coating that determines their color rather than the junction construction or chemistry.
I've never tried it but possibly the gate-source capcitance of a power MOSFET would work, I'm thinking that they generally have high capacitance to start with but I'm not sure how much it changes with applied reverse voltage.
Brian.