Hi, perhaps the following is of interest to instant shooters:
I have not tried this myself to confirm, but it appears that with some minor modifications Fujifilm FI-800GT instant film is usable in Kodak EK8 cameras.
The Fuji film is more sensitive than the Kodak camera wants it, so apparently a smaller aperture or ND filter is required.
Instructions on how to modify (in Japanese): http://island.geocities.jp/sihohigari/jp/tip/fi800.html
Fujifilm FI-800GT instant film is available only in Japan, but available via direct personal imports.