The big box stores should continue to carry rough service bulbs.
I wonder if "edison screw base heaters" would work. These are porcelain resistance heaters that have the same sort of screw base as a lightbulb.
Rather more expensive that a lightbulb (perhaps $20 to $30), but then you don't have to worry about them burning out.
The Edison bulbs are $11 at restoration hardware
Grainger carries the replacement bulbs for the Little Dipper, part ID is 5UCW0. I contacted Hilliards and they recommended this bulb. I bought 4 for under $15 total. They say they provide 20,000 hours each. Hope this helps!
Pet stores sell heater/ceramic bulbs in a wide range of power (used to keep dinosaurs warm).
Perfect for chocolate applications.