There are a gazillion places selling replacement bulbs. When the bulb went out on my Toshiba, I tried to do some homework.
Most of the really cheap places are selling raw bulbs and expecting the end user to place this in the old housing. When I took the old housing out, it actually broke as it had become brittle from all the heat.
The places that sold the entire lamp and housing were either within a few $$ of Toshiba, or I found discussion on how the housings were inferior and deformed in use.
In the end, I purchased from Toshiba. They sent the bulb out promptly and sent a return sticker for proper disposal of the mercury filled bulb. I felt it was a good deal in the end, especially since I got over 5k hours out of the old bulb and expect reasonable life from the new one. I worried that a cheap replacement bulb might have a significantly shorter life.