In article ,
R.P.McMurphy wrote:

.......... Can you suggest any actual components that
I could use for the heating/monitoring?

Rough calcs suggest that you need about 2-3 Watts
to raise that sized bar (20 sq inches) about 20C
above ambient. It looks rather low, so my calcs
could be wrong (probably are).

Might be worth looking at a tube, filled with oil,
heating resistor(s) and temperature sensor (diode?)
mounted at the bottom. Four wires coming out of the
bottom of the tube, which is to be solidly plugged,
and the top of the tube lightly plugged... enough
to hold the oil in, but something that allows air in
and out as the oil expands/contracts.

Temperature control circuitry mounted in the base.

--
Tony Williams.