I am not familiar with a filament that will meet that requirement. But then, I'm not that familiar with the variety of filaments out there. Now that we know what it is you need, One of our guru's here might be able to point in the right direction.

One place you might want to take a look is Smooth-On. They make a lot of different molding materials, one of which may fit your needs for your molds. You could use normal filament in a 3d printer to create your positive to cast the mold with, as most of the materials only require a vacuum pot. As you were planning on making the mold with a printer, then making the positive is the exact same process, just "mirrored".

Smooth on has what they call their high temp epoxy resin for mold making. It's rated to 375F, but from the description, Yours and theirs, it might be worth picking up a sample size bottle from them and give it a whirl.

Another method I know of, is using plaster of paris and play sand mixed to create molds. I'm planning to use this material in an Aluminum foundry in the near future.