Electronically controlled capacitors in the load network

I'm planning on building a polar transmitter based on WA1QIX's design. However, I would prefer to set up some kind of electronically controlled tuner capacitors so that I don't have to re-tune every time I switch bands. What kinds of electronic tuners are usable with the kinds of currents and voltages seen in a driver outputting a reasonable amount of wattage? Or should I resign myself to using a motor to turn a variable vacuum cap?