I buy regular wet clutch motorcycle oil. Usually the cheapest stuff they have,no additives and change it every ride or at least every other ride. Especially if you ride hard and use the clutch a lot. If you get in that habit, you'l notice if your losing oil and not ruin your transmission and it keeps you bottom end clean.

900ml of oil in the transmission. Which a quart of oil has 1000ml.

That's like buying 9 oil changes and getting the 10th free.