A little update, the seals you need for a Cagiva Canyon have the dimensions 45x58x11 mm. I have installed new seals from Athena (type: P40FORK455085, price: 17,50 euro)
Here some pictures (click for bigger format):
Opening the fork:
Remove everything from the fork:
The new seals (45x58x11):
The new seals in the sliders:
New front fork oil (SAE 7,5):
Ready: