Someone on this board reported them still being mastered and for sale in the UK. I also need some new rubber bands for inside the machine. It is beginning to slip a bit.
Don't know about the tapes, but for outstanding service, parts, repair and/or rebuilding of classic high-end audio equipment I highly recommend Soundsmith in New York. For tape decks they specialize in Tandberg, but can probably help you with your Akai as well.
They are so good that when necessary replacement parts are no longer available they manufacture their own. In my case they restored my 32-year-old Bang & Olufson Beogram 4002 turntable, including a new belt and motor. My phono cartridge/stylus was okay, but if I'd needed one they build their own (under license from B&O) which exceed the specs and performance of the B&O originals. I'd bet they have your Akai belts.
Here's the link: www.sound-smith.com
Thanks very much !