126 film is effectively discontinued, so finding fresh stock is unlikely. You may occasionally see old cartridges sold secondhand, but expired film can be unreliable.

A practical alternative is to reload an empty 126 cartridge with 35mm film. 126 film was essentially 35mm film packaged in a cartridge, so this can work if you load it in complete darkness (changing bag or darkroom). A shorter 24-exposure roll is usually preferred to avoid overfilling. Some people use unperforated film to avoid sprocket holes appearing in the image area.

For processing, the film can generally be developed with standard C-41 processing if you use color negative film. Printing may be trickier because 126 images are square, so not every lab will handle printing neatly from this format. You may need a lab familiar with older formats, or have the film developed and then scan or crop/print the images yourself.