All that is left new is consumer color neg. B and H has Kodak 400. I believe you can still get Fuji 200 at a few places. There is a guy who runs a site I came across several years ago who has stockpiled and frozen a ton of the Fuji Superia 200.
http://www.frugalphotographer.com/cat110.htm
It is a great film, although slower than some might want. There is also plenty of Ferrania, which is mostly repackaged as Wal-Mart, K-Mart, and whatever other store's brand. It is also available from that link above.
What most people do for their Pentax Auto 110s (and other such cameras) is buy a handful of rolls of whatever they can new, shoot what is there, and then save and reload the cassettes with their emulsions of choice. Hopefully you get cassettes that have the film-speed tab, so you can choose to leave it in place for high-speed films or remove it for low-speed films. If you get unlucky and get a 400 film with no tab, you have to rig a way to keep the lever inside the camera depressed, or you overexpose by two stops.
You can reload the cassettes with any cut down 120/220/70mm film, cut down 35mm non-perforated film, or just load it straight with 16mm movie film and incorporate the sprocket holes into the shooting. Some people like the sprocket holes, this is a very cheap way to get film, and it gives you some interesting emulsions to choose from without having to cut them down. Processing is an issue, though. You have to talk a movie film processing lab into running your little strips of film through their ECN or b/w reversal processes. You can get it with one row of holes or two.
Personally, I have just used 120 the couple of times I have shot black and white in my Auto 110. I developed ghetto style: in pitch darkness, running the film back and forth through a tray. I have seen some 110 reels for sale on EBay every now and then. That would be something worth looking into if you think you will load and process your own.
