Working Fluid for Higher Temperature Heat Pipe?

So after much research and thought I've decided not to pursue the construction of a heat pipe which works against gravity. It can be done, but the wick materials required to raise the fluid a meter a just a bit too demanding.

Instead I'll just elevate the receiving end so that it's higher than the hot end and use a gravity fed heat pipe.

My question now is on the working fluid. The 'cold' end will be boiling water, so will be at a minimum of 100ºC, too hot to re-condense water as a working fluid.

I need something which even at close to zero pressure has a boiling point over 100º, it needs to be easily sourceable and inexpensive. Also if it didn't smoke before it boiled, that'd be helpful.

Cheers,

Daniel.