Good morning, Ram;
At this time, Freestyle, B&H, Glazer's, Adorama, and others seem to be carrying the Fuji Instant Film Packs in 4 by 5 size; the FP-100C-45 and FP-3000B-45, color and black and white, respectively. The Fuji PA-45 Film Pack Holder is useful in this application.
It is true that Polaroid Corporation did stop making 4 by 5 instant film packs a few years back (around 6 or 8 years ago?), but it is possible that the IP (Impossible Project) people might resurrect that one also. Until that eventuality, we do have Fujiroid, as mentioned above.