Half-plate-size film is still made, for those who like to used their old cameras. I think I've avoided getting any film in that size, although I have holders (same size as 5x7" holders, for "normal" cameras).

Plate holders for old cameras can be a difficult thing to find. Not that there aren't lots of them to be found, but finding one that actually fits the camera you have is virtually impossible!

I've been lucky enough to get three fine 24x30cm holders with my big plate camera - all it needs is a new bellows. I've received a price estimate from Camera bellows, and it is very reasonable. Especially for a 34x34cm square bellows, with internal taper only, 24 pleats, max extension 85cm, minimum < 3.5cm...