There is a really good chance the Vista drivers will install, you just need to learn how to install them, probably. If I can get the XP drivers for my scanner to work, the Vista ones for you should work also. There is of course, a chance HP set them up so they would not work with Win 7 but there may be a way around that if it is the case. Usually this entails starting the install and copying the files from a temporary extraction location before you hit continue.
You may be able to install the files in Vista compatibility mode.
There may also be an .exe extractor that could get the files for you.
Another option might be running the Virtual XP machine under Windows 7.
But if it is easier getting another scanner, maybe it is...