Spare part 'protective anode' for old Vaillant cylinder?

Hi

I have an old but very reliable Vaillant boiler -C142 - it is accompanied by a floor standing storage cylinder.

I need a new 'protective anode' to fit into the top of this storage unit.

Is anybody able to point me in the right direction to acquire one?

There are a couple of numbers on a plate atop the unit. They are; Fab. No. 95 31083992 and VIH C120/3

Thank you in any event, for your time and consideration.

Best Wishes