On the subject of dew heaters,
here's a page with some info on Nichrome wire dew heaters using silicone tubing and a nice simple PWM cct using a 555 timer and a couple of extra components. I
built the circuit (for under $15 incl case) on veroboard and it works very well. It would be very simple to put the board inside the unused battery compartment of the LX90 Fahim.