Kodak doesn't make it anymore, but you can get their Super 8 cartridge on their website. There are only two reversal films though, so unless you want to pay to transfer negative film, that's all you can get from them.
Tri-XEktachrome 100DBut there are other films, Pro8mm takes various film stocks and repackages them into Super 8 cartridges, so you can now try some Fujichrome if you want.
Pro8mmFor processing, I've gone to
Spectra film and video, they also sell film for several formats, one I want to try is a Super 8 cartridge of Velvia 50.
As for the original point of pre-striped film, I did read an article in the Reel Image about someone making it in Spain. Though the price is pretty high, 39 Euros processing included for one cartridge of 100D.