I have an Impact Vision 24 that has a built-in SD/FF. Unfortunately it's only a 12-bit scandoubler and it doesn't handle all screenmodes (doesn't handle VGAOnly at all, even with the scandoubler switch set to the off position which theoretically should just pass through the signal to the HD-15 connector). Not sure if it's of any interest to you.
I'm kind of loathe to part with it since I was hoping to take some RGB screengrabs from some game consoles with it, but I don't have the RGB input module so it seems unlikely I'll ever use it for that so I might be willing to trade.
