Clutch slave is most likely in my experience. You could try topping the container back up and check for leaks with paper towel etc but it is nasty stuff.
Brembo dont like end users rebuilding their kits, powerhouse in the UK sell do sell caliper seal kits so you could try them: https://www.ebay.co.uk/itm/Ducati-Su...t/151102161905
Less time consuming would be a new slave, Oberon do some really nice units.
Installing Banjo bolts with extra bleed nipples can make bleeding a lot easier / faster.