Your best bet might be to come off the HDMI out of your computer into an adapter. Adapters are inexpensive.
Before we go further, I'm assuming you've tested the projector and it is functioning properly. It is certainly not worth putting any money into it, especially an expensive bulb.
I guess you're trying to use it for home theater. You'll probably be pretty disappointed with the picture quality, especially if you've seen a more modern projector. I think these types of projectors are OK for PowerPoint presentations, but not so much for movies.