My house has several wall-mounted gas heaters. All but one of them have external, easily accessible thermostats. However, the one that happens to be the most used has no remotely mounted thermostat, to change the temperature you have to open the cover at the base, and adjust a knob at the base of the heater. Is there any way to retrofit this heater with a simple remote thermostat? Ideally, I'd like something really simple. All the other heaters I have just use contact-closure (e.g. 2 wire, I think) thermostats, not the programmable electronic kinds, and that's all I really want for this heater too. The heater doesn't currently have any connections for electrical, so an Ideal solution would not require any electrical power. However, I'm not sure if this is possible. I can run power to the heater if I have to, but I'd sure like to avoid any drywall work. Heater pictures:
The whole burner assembly is completely separate from the actual heater. It looks like the whole burner, with valve assembly, can be separated from the heater with the removal of just two screws. Anyways, the heater model is a Williams 35 GV-C-5T NAT (I think. See picture):
The burner assembly and valve is a RobertShaw Grayson 7000 SRLC:
Of note is that on the instruction plates in the heater, there are several diagrams that show a similar valve that supports a remote thermostat: 
However, in both cases, the images are for a 7000 M VRLC or M VRCLC, while the heater I have is a S RLC.
