If I'm remembering correctly, a few years back Dave Barker @ VPI posted a how-to diagram for modifying home based thermos that you can buy in home depot to work with oil-filled heaters and other AC based non-motorized heat sources. At the time I believe that VPI was using them in their walk-in incubator to incubate all of their eggs that they produce every year with great success. You might want to poke around on www.vpi.com for a contact e-mail and see if this is the case. It doesn't hurt to ask.

Hope this helps.

-adam