I don't want to stress you, but be careful with who you buy from. You will want to find a OEM replacement from a reputable dealer, you might find a quality OEM-compatible but be sure it has a good reputation if you go that way. (there are chinese knockoffs that fail more often out there) You can still find those that are discounted that way but you should probably check with Toshiba on how much they have them for also. Also there are two ways to buy. Those that are bare bulbs that you have to put in the old casing. (cheaper but probably not for you) or ones that come with a new casing. Also use a glove when touching the bulb and casing. Oils from your skin can cause them to fail prematurely.
To find reputable dealers I would recommend asking those who also own your model of tv on a messageboard like avsforum.