I have seen this done (my boss did it with a small tear in his VFR750 seat).
1. Turn the seat over. You should have a small amount of spare material where the cover has been stretched and stapled.
2. Cut off a small piece of the spare material - enough to cover the tear (like a puncture repair)
3. Carefully push the spare material into the tear. Use a matchstick or the blunt end of a plastic spoon.
4. Once the material is between the tear and the foam, superglue around the edges.
This makes a waterproof and almost invisible* repair.
* Disclaimer... The "invisibleness" of the repair is directly proportional to the amount of care that you use. Do not use too much glue as it will show through the remaining tear (where the edges don't quite meet).
Good luck.
Steve