Lamps are indeed somthing of a shell game. Find the oem bulb manufacturer...the actual bulb. It may be for examplr a Phillips. If that is correct or another name brand bulb, be sure your replacement is the same.
Now, you mentioned "I need to replace the lamp". If you are getting a "replace lamp" message but the pj is still lit, make a note of the hours and then in the user menu there will be a " have you replaced" the lamp message. Just confirm you have and the message will disappear until you rack up another 2000 hours or so.
That being said, it is still prudent to have a spare lamp on hand always so buy one now. You do not have to replace it until it either becomes too dim or fails altogether. You could replace it with your new one and keep the used but functional lamp as a backup.
Lamps can last a lot longer than you might think from reading the literature that came with your pj. I have reset the clock on many projectors and am currently at 6000 hours on my present system. It still produces over 20fl when pressed, but I prefer the standard 16 fl so that is where it is set.
Major lamp killer? Repeated power cycles. If I am going to be usingy system for the day varying between games/films or whole house sound where the pj really need not be on, I leave in on anyway rather than cycling power.