You could find a beater Speed Graphic and hack together a back (the "Pack Film" backs for the terribly obsolete conventional film in packs are $free to $10 on eBay or here) to suit. Then you'd have Fuji FP100C available, easy fast sync with the front shutter (leaf shutter, so up to 1/500th) and a helluva conversation piece. Just need a flash bracket or a "potato masher" electronic flash.
I have a 4x5 Speed setup to shoot 3x4 Fujiroids, if I shoot it a bunch I can even use tilt without wasting film and just using the rangefinder and viewfinder that are built in. I usually give away the shots I take with it.
Barring that, I'd still try to find a way to make Fujiroids work but Instax is a great film. I just don't like the camera.