It's nearly 15 years old. You'll have to search and MAYBE get lucky.
You can backsave any AI file from the current version to an AI8 file at any time. Why restrict yourself to an old version the use of which in Windows 7 is problematic.
It won't run on Win 7, anyway and as Scott said, finding such old versions in working condition will be almost impossible to begin with. As larry said, simply use any current vector editing program. The all can save/ export AI88 files.