This bulb is made for traffic signals. They are designed to cycle on/off constantly. That is very hard on regular light bulbs, and they tend to burn out fast. I AM NOT recommending this site as I know nothing about them, it just happens to be where I found an example of the bulb. I bought mine at the local electric supply store. Sylvania and Phillips both make this bulb. They are common bulbs if you know what to ask for. I put one in my incubator and it seems to be doing the job just fine so far. Hope this helps.
https://www.interlight.biz/light-bulb/40A/TS&ID=FROOGLE-US
https://www.interlight.biz/light-bulb/40A/TS&ID=FROOGLE-US

