If the ambient air temperature remains somewhat constant, the liquid will get there eventually. I haven't opened my Lasko heater up yet, but since there is a thermostat wired in series with the heater, maybe the external t-stat is the only one you want to use. Hint, hint, wink, wink. I'm just not sayin' well you know.
I did once upon a time have my fermenter on the bottom shelf, and my Lasko on the top shelf. The air was really hot, but the wort wasn't yet.
How about this: an electric heating pad. I have no idea how hot it will get, as I don't ferment at high temperatures, but you may want to try it. There are quite a few of us that use heating pads for "odd" applications. You will of course, need an older style heating pad that does not have a timer built into it. They are getting a bit scarce to find for what I have looked.