here's a tip for you Minolta 16 shooters -- you don't actually need a cartridge to use those cameras. If you take a length of 16mm film (about 20 inches, I believe) you can coil it up on the supply side of the film chamber, tape the end to the take-up shaft on the other side (all this is in total darkness, of course) close it up and away you go -- you have to take the film out in a darkroom too, but if you just want to give the thing a try, this works.
If you do this, fire off about 5 blanks -- frame spacing on those is usually done by a cam that compensates as the take-up roll gets fatter, but the take up shaft is thinner than what the cam is designed for, so you need to compensate more.
if you go to submini.org you can find sources for film, or make a cheap slitter (i once made one out of a couple blocks of wood, a door hinge and some felt and razor blades) and make your own.