Second suggestion is buy new, Crewe Audi will eventually be back working, not long now I think. Unfortunately the pipe does not seem available separately and you have to buy the filling hopper in the service hatch as well since the pipe appears bonded to it, to say nothing of the labour.
windscreen washer system Audi A2 (A2) 2003 year Audi EUROPA 955010 spare parts
audi.7zap.com
Third suggestion is bodge it.
The suggestion of sealant may work, it very much depends on the nature of the crack, after all as I see it any water pressure and leak is only transient during filling.
Alternatively it strikes me you may be able to repair somehow with corrugated hose intended for connecting garden water butts (garden centres are strangely now open!). A rough measure of the A2 pipe is somewhere near 28.5mm OD which is in the the same ball park as the common 25mm (ID I think) water butt hose. You might get away with cutting the pipe at the crack and using a connector, but without further details it is difficult to say.
Barbed Hose connector Straight piece union available in a range of sizes, useful when joining pieces of hose. Picture may vary.
www.freeflush.co.uk
Just an idea, feasibility needs assessment.
Andy